chore(data,engine,docs): remove Google Play Games Services sync backend

Deletes the solitaire_gpgs crate and all GPGS references from settings,
sync client, profile plugin, CLAUDE.md, and ARCHITECTURE.md. The
self-hosted server covers all sync needs without the Android-only backend.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ARCHITECTURE.md

@@ -16,28 +16,25 @@
 5. [Game Engine Architecture](#5-game-engine-architecture)
 6. [Persistence & Sync Architecture](#6-persistence--sync-architecture)
 7. [Sync Server Architecture](#7-sync-server-architecture)
-8. [Google Play Games Services (Android Future)](#8-google-play-games-services-android-future)
+8. [Data Models](#8-data-models)
-9. [Data Models](#9-data-models)
+9. [API Reference](#9-api-reference)
-10. [API Reference](#10-api-reference)
+10. [Merge Strategy](#10-merge-strategy)
-11. [Merge Strategy](#11-merge-strategy)
+11. [Achievement System](#11-achievement-system)
-12. [Achievement System](#12-achievement-system)
+12. [Progression System](#12-progression-system)
-13. [Progression System](#13-progression-system)
+13. [Audio System](#13-audio-system)
-14. [Audio System](#14-audio-system)
+14. [Asset Pipeline](#14-asset-pipeline)
-15. [Asset Pipeline](#15-asset-pipeline)
+15. [Platform Targets](#15-platform-targets)
-16. [Platform Targets](#16-platform-targets)
+16. [Build & Development Guide](#16-build--development-guide)
-17. [Build & Development Guide](#17-build--development-guide)
+17. [Deployment Guide](#17-deployment-guide)
-18. [Deployment Guide](#18-deployment-guide)
+18. [Security Model](#18-security-model)
-19. [Security Model](#19-security-model)
+19. [Testing Strategy](#19-testing-strategy)
-20. [Testing Strategy](#20-testing-strategy)
+20. [Decision Log](#20-decision-log)
-21. [Decision Log](#21-decision-log)
 
 ---
 
 ## 1. Project Overview
 
-Solitaire Quest is a cross-platform Klondike Solitaire game written in Rust, targeting macOS, Windows, and Linux desktops (iOS/Android as a stretch goal). It features a full progression system with XP, levels, achievements, daily challenges, and an optional self-hosted sync server so statistics and progress are available across all of a player's devices.
+Solitaire Quest is a cross-platform Klondike Solitaire game written in Rust, targeting macOS, Windows, and Linux desktops. It features a full progression system with XP, levels, achievements, daily challenges, and an optional self-hosted sync server so statistics and progress are available across all of a player's devices.
-
-On Android (stretch goal), sync is enhanced with Google Play Games Services (GPGS) for native achievement popups, leaderboards, and cloud saves — sitting on top of the same underlying sync payload so data stays consistent regardless of which backend was used last.
 
 ### Sync Backend by Platform
 
@@ -46,8 +43,6 @@ On Android (stretch goal), sync is enhanced with Google Play Games Services (GPG
 | macOS | Self-hosted server | Full feature set |
 | Windows | Self-hosted server | Full feature set |
 | Linux | Self-hosted server | Full feature set |
-| Android (stretch) | Google Play Games Services | + server as fallback |
-| iOS (stretch) | Self-hosted server | GPGS not supported on iOS |
 
 ### Design Principles
 
@@ -91,7 +86,6 @@ solitaire_quest/
 ├── solitaire_data/             # Persistence, sync client, settings
 ├── solitaire_engine/           # Bevy ECS systems, components, plugins
 ├── solitaire_server/           # Self-hosted sync server (Axum + SQLite)
-├── solitaire_gpgs/             # Google Play Games Services bridge (Android only, stub until stretch goal)
 └── solitaire_app/              # Main binary entry point
 ```
 
@@ -135,22 +129,7 @@ Owns:
 - `SyncBackend` enum and backend selection
 - Solitaire Server sync client (JWT auth, auto-refresh)
 - OS keychain integration (`keyring`)
-- `SyncProvider` trait — implemented by both `SolitaireServerClient` and `GpgsClient` (Android)
+- `SyncProvider` trait — implemented by `SolitaireServerClient`
-
-### `solitaire_gpgs` *(stub — implement when targeting Android)*
-**Dependencies:** `solitaire_sync`, `jni` (Android only), `solitaire_data` trait impls.
-
-Android-only crate, compiled only when `target_os = "android"`. Bridges the Google Play Games Services Java SDK via JNI.
-
-Owns:
-- `GpgsClient` implementing the `SyncProvider` trait from `solitaire_data`
-- GPGS Saved Games API calls (load/save cloud save slot)
-- GPGS Achievements API calls (unlock, reveal, increment)
-- GPGS Leaderboards API calls (submit score, load scores)
-- Google Sign-In token management (via JNI into Android SDK)
-- Conversion between GPGS cloud save blob ↔ `SyncPayload`
-
-> **Note:** This crate contains only a trait stub and compile-time stub implementations until Android support is actively developed. Do not implement JNI bindings until Phase: Android.
 
 ### `solitaire_engine`
 **Dependencies:** `bevy`, `bevy_kira_audio`, `solitaire_core`, `solitaire_data`.
@@ -223,8 +202,7 @@ SyncPlugin::on_startup()
     │  spawns AsyncComputeTask
     ▼
 solitaire_data::sync_pull()          ← dispatches to active SyncProvider
-    │                                    SolitaireServerClient  (desktop / iOS)
+    │                                    SolitaireServerClient
-    │                                    GpgsClient             (Android, future)
     ▼
 solitaire_sync::merge(local, remote)
     │
@@ -245,7 +223,7 @@ SyncPlugin::on_exit()
     │  blocking push (acceptable on exit, not on main loop)
     ▼
 active SyncProvider::push(local)
-    │  POST to server  — or —  GPGS Saved Games PUT (Android)
+    │  POST to server
     ▼
 Done
 ```
@@ -382,7 +360,6 @@ Implementations:
 |---|---|---|
 | `LocalOnlyProvider` | No-op (default) | All |
 | `SolitaireServerClient` | Self-hosted server | All |
-| `GpgsClient` *(future)* | Google Play Games Services | Android only |
 
 Sync always runs on `bevy::tasks::AsyncComputeTaskPool` — the game thread is never blocked.
 
@@ -397,9 +374,6 @@ pub enum SyncBackend {
         // JWT access + refresh tokens stored in OS keychain
         // key: "solitaire_quest_server_{username}"
     },
-    GooglePlayGames,
-    // No credentials stored locally — auth managed by Google Sign-In SDK via JNI
-    // Android only; selecting this on non-Android falls back to Local silently
 }
 ```
 
@@ -411,10 +385,6 @@ On exit: `POST /api/sync/push` with payload
 On 401: automatically attempt `POST /api/auth/refresh`, retry once, then surface error to user.
 Credentials stored in OS keychain via `keyring` — never in plaintext on disk.
 
-### Google Play Games Sync *(Android — future, see Section 8)*
-
-Implemented in `solitaire_gpgs` crate. Uses the GPGS Saved Games API with named slot `"solitaire_quest_sync"`. The `GpgsClient` struct implements `SyncProvider` — the `SyncPlugin` treats it identically to `SolitaireServerClient`. The same `solitaire_sync::merge()` function applies regardless of which provider returned the remote data.
-
 ---
 
 ## 7. Sync Server Architecture
@@ -501,89 +471,7 @@ This ensures all players worldwide get the same challenge for a given date, rega
 
 ---
 
-## 8. Google Play Games Services (Android Future)
+## 8. Data Models
-
-> **Status: Stub only.** Do not implement JNI bindings until Android is actively targeted. The `solitaire_gpgs` crate exists in the workspace with a trait stub so the compiler enforces the interface contract from day one.
-
-### Why GPGS on Android
-
-Google Play Games Services provides first-class Android features that would otherwise require significant backend work:
-
-| Feature | GPGS Provides | Our Alternative |
-|---|---|---|
-| Cloud saves | Saved Games API | Self-hosted server |
-| Achievements | Native popups + Play profile | In-game toasts only |
-| Leaderboards | Hosted by Google, visible in Play app | Server leaderboard |
-| Auth | Google Sign-In, no registration | Username + password |
-
-On Android, GPGS is the **primary** sync provider. The self-hosted server is the **fallback** if the player is not signed in or has no server configured. Both can be active simultaneously — a win pushes to both, pull merges from whichever responded last.
-
-### Compatibility Reality
-
-| Platform | GPGS Support |
-|---|---|
-| Android | ✅ Full |
-| Windows | ✅ GPGS for PC (optional, separate SDK) |
-| macOS | ❌ Not supported |
-| Linux | ❌ Not supported |
-| iOS | ❌ Not supported |
-
-macOS, Linux, and iOS users always use the self-hosted server. This is why the server is the primary design and GPGS is an enhancement layer.
-
-### `solitaire_gpgs` Crate Design
-
-The crate is compiled only on Android (`#[cfg(target_os = "android")]`). On all other platforms the crate exports only the stub.
-
-```rust
-// solitaire_gpgs/src/lib.rs
-
-#[cfg(target_os = "android")]
-mod android;
-
-#[cfg(not(target_os = "android"))]
-mod stub;
-
-pub use stub::GpgsClient;   // stub on desktop
-#[cfg(target_os = "android")]
-pub use android::GpgsClient; // real impl on Android
-```
-
-### JNI Bridge (Android implementation — future)
-
-The real `GpgsClient` uses the `jni` crate to call into the GPGS Android SDK:
-
-```
-Rust GpgsClient
-    │  jni::JNIEnv
-    ▼
-Java: com.google.android.gms.games.PlayGames
-    ├── getSnapshotsClient()   → Saved Games (sync payload)
-    ├── getAchievementsClient() → unlock / reveal
-    └── getLeaderboardsClient() → submit score
-```
-
-Steps required when Android work begins:
-1. Add `cargo-mobile2` to the build toolchain
-2. Implement `GpgsClient` with `jni` bindings in `solitaire_gpgs/src/android.rs`
-3. Add `GpgsClient: SyncProvider` impl — pull/push map to Saved Games load/save
-4. Mirror achievement unlocks: on `AchievementUnlockedEvent`, call GPGS unlock API alongside in-game toast
-5. Submit scores to GPGS leaderboard on `GameWonEvent`
-6. Add Google Sign-In button to the Settings screen (Android build only, `#[cfg]` gated)
-
-### Dual-Sync on Android
-
-When both GPGS and the self-hosted server are configured, the `SyncPlugin` runs both providers concurrently and merges all three payloads (local + GPGS + server) using the same `solitaire_sync::merge()` function applied twice:
-
-```
-local ──────┐
-             ├── merge() ──► intermediate ──┐
-gpgs ────────┘                               ├── merge() ──► final
-                                server ──────┘
-```
-
----
-
-## 9. Data Models
 
 ### Core Game Models (`solitaire_core`)
 
@@ -677,14 +565,14 @@ pub struct Settings {
     pub music_volume: f32,
     pub animation_speed: AnimSpeed,
     pub theme: Theme,
-    pub sync_backend: SyncBackend, // Local | SolitaireServer | GooglePlayGames
+    pub sync_backend: SyncBackend, // Local | SolitaireServer
     pub first_run_complete: bool,
 }
 ```
 
 ---
 
-## 10. API Reference
+## 9. API Reference
 
 All endpoints are under the base URL configured by the user (e.g., `https://solitaire.example.com`).
 
@@ -727,9 +615,9 @@ All endpoints are under the base URL configured by the user (e.g., `https://soli
 
 ---
 
-## 11. Merge Strategy
+## 10. Merge Strategy
 
-Used identically by the `SolitaireServerClient`, `GpgsClient`, and server-side handler. Lives in `solitaire_sync` as a pure function with no I/O. Called once per provider when multiple backends are active simultaneously (e.g. GPGS + server on Android).
+Used by both `SolitaireServerClient` and the server-side handler. Lives in `solitaire_sync` as a pure function with no I/O.
 
 ```rust
 pub fn merge(local: &SyncPayload, remote: &SyncPayload) -> SyncPayload {
@@ -769,7 +657,7 @@ pub fn merge(local: &SyncPayload, remote: &SyncPayload) -> SyncPayload {
 
 ---
 
-## 12. Achievement System
+## 11. Achievement System
 
 ### Definition Structure
 
@@ -814,13 +702,9 @@ pub struct AchievementDef {
 
 Achievement conditions are evaluated by `AchievementPlugin` on every `GameWonEvent` and `StateChangedEvent`. The plugin calls `solitaire_core::check_achievements()` which returns a `Vec<AchievementDef>` of newly unlocked achievements. The plugin then fires `AchievementUnlockedEvent` for each, which the toast and persistence systems handle independently.
 
-### GPGS Mirroring *(Android, future)*
-
-When the `GpgsClient` is active, every `AchievementUnlockedEvent` also triggers a GPGS `achievements.unlock()` call via JNI so the achievement appears in the player's Google Play profile. A static map in `solitaire_gpgs` maps our achievement IDs to GPGS achievement IDs (assigned in the Google Play Console). Mirroring is fire-and-forget — failures are logged but never block the in-game toast.
-
 ---
 
-## 13. Progression System
+## 12. Progression System
 
 ### XP Sources
 
@@ -849,7 +733,7 @@ Levels 11+:   level = 10 + floor((total_xp - 5000) / 1000)
 
 ---
 
-## 14. Audio System
+## 13. Audio System
 
 Audio uses `bevy_kira_audio`. All sound files are `.wav`.
 
@@ -868,7 +752,7 @@ Audio systems listen for Bevy events and never block the game thread.
 
 ---
 
-## 15. Asset Pipeline
+## 14. Asset Pipeline
 
 All assets are loaded through Bevy's `AssetServer`. No bytes are hardcoded in source.
 
@@ -890,21 +774,21 @@ Card backs: `assets/cards/backs/back_0.png` through `back_4.png`. Additional bac
 
 ---
 
-## 16. Platform Targets
+## 15. Platform Targets
 
 | Platform | Status | Primary Sync | Notes |
 |---|---|---|---|
 | macOS | Primary | Self-hosted server | x86_64 + Apple Silicon (universal binary via `cargo-lipo`) |
-| Windows | Primary | Self-hosted server | x86_64, MSVC toolchain; optional GPGS for PC (future) |
+| Windows | Primary | Self-hosted server | x86_64, MSVC toolchain |
 | Linux | Primary | Self-hosted server | x86_64, tested on Ubuntu 22.04+ and Fedora 39+ |
-| Android | Stretch | Google Play Games + server | `cargo-mobile2`, touch input, GPGS via JNI |
+| Android | Stretch | Self-hosted server | `cargo-mobile2`, touch input |
-| iOS | Stretch | Self-hosted server | `cargo-mobile2`, touch input; GPGS unavailable on iOS |
+| iOS | Stretch | Self-hosted server | `cargo-mobile2`, touch input |
 
 Minimum Bevy window size enforced: 800×600. Desktop windows are freely resizable; layout recomputes on `WindowResized`.
 
 ---
 
-## 17. Build & Development Guide
+## 16. Build & Development Guide
 
 ### Prerequisites
 
@@ -965,7 +849,7 @@ Add `--features bevy/dynamic_linking` during development to dramatically reduce
 
 ---
 
-## 18. Deployment Guide
+## 17. Deployment Guide
 
 ### Docker Compose (Recommended)
 
@@ -1010,7 +894,7 @@ Migrations run automatically on startup via `sqlx::migrate!()`.
 
 ---
 
-## 19. Security Model
+## 18. Security Model
 
 | Concern | Mitigation |
 |---|---|
@@ -1026,7 +910,7 @@ Migrations run automatically on startup via `sqlx::migrate!()`.
 
 ---
 
-## 20. Testing Strategy
+## 19. Testing Strategy
 
 ### Unit Tests (`solitaire_core`)
 
@@ -1065,12 +949,10 @@ Using `axum::test` and an in-memory SQLite database:
 - [ ] Achievement toast appears and dismisses
 - [ ] Server sync: register, login, push, pull on second machine
 - [ ] Server sync: JWT refresh on 401 works transparently
-- [ ] GPGS sync (Android only): sign in, unlock achievement, verify appears in Play Games app
-- [ ] Dual sync (Android only): GPGS + server both configured, payloads merge correctly
 
 ---
 
-## 21. Decision Log
+## 20. Decision Log
 
 | Decision | Rationale | Date |
 |---|---|---|
@@ -1082,7 +964,6 @@ Using `axum::test` and an in-memory SQLite database:
 | bcrypt cost 12 | Balances security and registration latency (~300ms on modern hardware); higher than default 10 | 2026-04-19 |
 | No email required for server accounts | Reduces PII collected; simplifies self-hosted deployments; password reset handled by server admin if needed | 2026-04-19 |
 | Self-hosted server as primary sync (not WebDAV) | A proper Rust server gives us auth, leaderboards, and daily challenge seeding for minimal extra effort over WebDAV, and removes a redundant backend | 2026-04-20 |
-| `SyncProvider` trait, not `SyncBackend` match arms | Allows adding Google Play Games Services cleanly; `SyncPlugin` stays backend-agnostic and testable | 2026-04-20 |
+| `SyncProvider` trait, not `SyncBackend` match arms | `SyncPlugin` stays backend-agnostic and testable; new backends can be added without touching the plugin | 2026-04-20 |
-| GPGS as Android enhancement, not replacement | GPGS has no macOS/Linux support; the server must remain universal, with GPGS layered on top for Android players | 2026-04-20 |
 | Dropped WebDAV backend | Redundant once the self-hosted server exists; removing it reduces surface area and simplifies settings UI | 2026-04-20 |
-| `solitaire_gpgs` crate stubbed from day one | Enforces the `SyncProvider` interface contract at compile time even before Android work begins; avoids architectural rework later | 2026-04-20 |
+| Dropped GPGS backend | Redundant with the self-hosted server; adds JNI complexity for no user-visible benefit on the target platforms | 2026-04-28 |

CLAUDE.md

@@ -12,7 +12,6 @@ solitaire_sync/    # Shared API types — NO Bevy, serde/uuid/chrono only
 solitaire_data/    # Persistence + SyncProvider trait + server client
 solitaire_engine/  # Bevy ECS systems, components, plugins
 solitaire_server/  # Axum sync server binary
-solitaire_gpgs/    # Google Play Games bridge — STUB ONLY until Android phase
 solitaire_app/     # Thin binary entry point
 assets/            # Source assets — embedded at compile time via include_bytes!()
 ```
@@ -53,7 +52,6 @@ cargo clippy -p solitaire_core -- -D warnings
 - Passwords and tokens are stored in the OS keychain via the `keyring` crate — never in plaintext files or logs.
 - Sync runs on `AsyncComputeTaskPool` — never block the Bevy main thread.
 - All sync backends implement the `SyncProvider` trait. The `SyncPlugin` is backend-agnostic — never `match` on `SyncBackend` inside a Bevy system.
-- `solitaire_gpgs` is a stub until Android work begins. Do not write JNI bindings yet; keep the compile-time stub so the trait contract is enforced from day one.
 - `cargo clippy --workspace -- -D warnings` must pass clean after every change.
 - `cargo test --workspace` must pass after every change.
 

Cargo.lock

@@ -6664,15 +6664,6 @@ dependencies = [
  "uuid",
 ]
 
-[[package]]
-name = "solitaire_gpgs"
-version = "0.1.0"
-dependencies = [
- "async-trait",
- "solitaire_data",
- "solitaire_sync",
-]
-
 [[package]]
 name = "solitaire_server"
 version = "0.1.0"

Cargo.toml

@@ -5,7 +5,6 @@ members = [
     "solitaire_data",
     "solitaire_engine",
     "solitaire_server",
-    "solitaire_gpgs",
     "solitaire_app",
     "solitaire_assetgen",
 ]

solitaire_data/src/settings.rs

@@ -40,7 +40,8 @@ pub enum Theme {
 
 /// Which sync backend the player has configured.
 ///
-/// JWT tokens for `SolitaireServer` are stored in the OS keychain via
+/// `Local` keeps all progress on-device. `SolitaireServer` syncs via the
+/// self-hosted server. JWT tokens are stored in the OS keychain via
 /// `solitaire_data::auth_tokens` — **never** in this struct.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
 pub enum SyncBackend {
@@ -57,10 +58,7 @@ pub enum SyncBackend {
         username: String,
         // JWT tokens are stored in the OS keychain — not here.
     },
-    /// Google Play Games Services (Android only). Selecting this on non-Android
+
-    /// platforms silently falls back to `Local` at runtime.
-    #[serde(rename = "google_play_games")]
-    GooglePlayGames,
 }
 
 /// Persistent user settings.

solitaire_data/src/sync_client.rs

@@ -412,19 +412,12 @@ async fn extract_push_body(resp: reqwest::Response) -> Result<SyncResponse, Sync
 /// This is the **one** place in the codebase that matches on [`SyncBackend`]
 /// variants. All other code receives a `Box<dyn SyncProvider + Send + Sync>`
 /// and remains backend-agnostic.
-///
-/// `GooglePlayGames` is Android-only; on desktop it silently falls back to
-/// [`LocalOnlyProvider`].
 pub fn provider_for_backend(backend: &SyncBackend) -> Box<dyn SyncProvider + Send + Sync> {
     match backend {
         SyncBackend::Local => Box::new(LocalOnlyProvider),
         SyncBackend::SolitaireServer { url, username } => {
             Box::new(SolitaireServerClient::new(url.clone(), username.clone()))
         }
-        SyncBackend::GooglePlayGames => {
-            // GPGS is Android-only; fall back to no-op on desktop.
-            Box::new(LocalOnlyProvider)
-        }
     }
 }
 
@@ -470,12 +463,6 @@ mod tests {
         assert_eq!(provider.backend_name(), "local");
     }
 
-    #[test]
-    fn factory_gpgs_falls_back_to_local() {
-        let provider = provider_for_backend(&SyncBackend::GooglePlayGames);
-        assert_eq!(provider.backend_name(), "local");
-    }
-
     #[test]
     fn factory_server_returns_server_client() {
         let provider = provider_for_backend(&SyncBackend::SolitaireServer {

solitaire_engine/src/profile_plugin.rs

@@ -260,7 +260,6 @@ fn sync_info(backend: &SyncBackend) -> (&'static str, String) {
         SyncBackend::SolitaireServer { username, .. } => {
             ("Solitaire Server", username.clone())
         }
-        SyncBackend::GooglePlayGames => ("Google Play Games", "—".to_string()),
     }
 }
 

solitaire_gpgs/Cargo.toml

@@ -1,10 +0,0 @@
-[package]
-name    = "solitaire_gpgs"
-version.workspace = true
-license.workspace = true
-edition.workspace = true
-
-[dependencies]
-solitaire_data = { workspace = true }
-solitaire_sync = { workspace = true }
-async-trait    = { workspace = true }

solitaire_gpgs/src/android.rs

@@ -1,12 +0,0 @@
-// TODO (Phase: Android) — implement JNI bindings here.
-//
-// Steps:
-// 1. Add `jni` dependency under [target.'cfg(target_os = "android")'.dependencies]
-// 2. Implement GpgsClient using cargo-mobile2 JNI bridge
-// 3. pull():  call PlayGames.getSnapshotsClient().open("solitaire_quest_sync")
-//             -> deserialize JSON blob into SyncPayload
-// 4. push():  serialize SyncPayload to JSON -> write to Saved Game slot
-// 5. mirror_achievement(id): call PlayGames.getAchievementsClient().unlock(map_id(id))
-// 6. Maintain a static ID mapping: our &str IDs -> GPGS achievement IDs (from Play Console)
-// 7. On GameWonEvent, submit score to GPGS leaderboard
-// 8. Add Google Sign-In button to Settings screen (Android build only, #[cfg] gated)

solitaire_gpgs/src/lib.rs

@@ -1,11 +0,0 @@
-#[cfg(target_os = "android")]
-mod android;
-
-#[cfg(not(target_os = "android"))]
-mod stub;
-
-#[cfg(not(target_os = "android"))]
-pub use stub::GpgsClient;
-
-#[cfg(target_os = "android")]
-pub use android::GpgsClient;

solitaire_gpgs/src/stub.rs

@@ -1,71 +0,0 @@
-use async_trait::async_trait;
-use solitaire_data::{SyncError, SyncProvider};
-use solitaire_sync::{ChallengeGoal, LeaderboardEntry, SyncPayload, SyncResponse};
-
-/// Google Play Games Services sync client — desktop/iOS stub.
-///
-/// Always returns [`SyncError::UnsupportedPlatform`]. The real JNI implementation
-/// lives in `android.rs` and is compiled only on Android (Phase: Android).
-pub struct GpgsClient;
-
-impl GpgsClient {
-    /// Creates a new `GpgsClient` stub. No-op on non-Android platforms.
-    pub fn new() -> Self {
-        Self
-    }
-}
-
-impl Default for GpgsClient {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-#[async_trait]
-impl SyncProvider for GpgsClient {
-    async fn pull(&self) -> Result<SyncPayload, SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    async fn push(&self, _payload: &SyncPayload) -> Result<SyncResponse, SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    fn backend_name(&self) -> &'static str {
-        "Google Play Games (unavailable on this platform)"
-    }
-
-    fn is_authenticated(&self) -> bool {
-        false
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn mirror_achievement(&self, _id: &str) -> Result<(), SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn fetch_leaderboard(&self) -> Result<Vec<LeaderboardEntry>, SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn fetch_daily_challenge(&self) -> Result<Option<ChallengeGoal>, SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn opt_in_leaderboard(&self, _display_name: &str) -> Result<(), SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn opt_out_leaderboard(&self) -> Result<(), SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-
-    /// No-op stub — returns UnsupportedPlatform on non-Android targets.
-    async fn delete_account(&self) -> Result<(), SyncError> {
-        Err(SyncError::UnsupportedPlatform)
-    }
-}