feat(engine): add New Game UI button in HUD

Per the UI-first design principle (CLAUDE.md, ARCHITECTURE.md §1),
every player action must be reachable from a visible UI control with
the keyboard shortcut as an optional accelerator. Add a top-right
"New Game" button that fires NewGameRequestEvent on click; the
existing ConfirmNewGameScreen modal in GamePlugin handles the abandon-
current-game confirmation flow when a game is already in progress.

- NewGameButton marker component, BackgroundColor-styled with idle /
  hover / pressed states.
- spawn_new_game_button startup system anchors the button at the top
  right of the window using absolute positioning.
- handle_new_game_button reads Changed<Interaction> on Pressed and
  writes NewGameRequestEvent::default(); paint_new_game_button
  applies the colour for the current state.

The N key still works as an accelerator. The legacy
NewGameConfirmEvent toast / countdown machinery in InputPlugin is
left in place for now — the button gives players a discoverable
path that bypasses the toast/modal collision reported during the
2026-04-29 smoke test.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ARCHITECTURE.md

@@ -51,6 +51,7 @@ Solitaire Quest is a cross-platform Klondike Solitaire game written in Rust, tar
 - **No panics in game logic.** Every state transition returns `Result<_, MoveError>`. Panics are only acceptable in startup/configuration code.
 - **One language, one repo.** The game client, sync client, shared types, and sync server are all Rust crates in a single Cargo workspace.
 - **Plugin-based Bevy architecture.** Each major feature is a Bevy `Plugin`. Systems are small and single-purpose. Cross-system communication uses Bevy `Event`s.
+- **UI-first interaction.** Every player-triggered action — new game, undo, draw, pause, open stats / settings / help / profile / leaderboard, etc. — must be reachable from a visible UI control. Keyboard shortcuts exist only as optional accelerators for power users; they are never the sole entry point. A player using only mouse or touch must be able to perform every action. New gameplay features ship with the UI control alongside the system that backs it.
 
 ---
 
@@ -67,11 +68,11 @@ solitaire_quest/
 ├── Dockerfile                  # Multi-stage server build
 ├── docker-compose.yml          # Server + Caddy reverse proxy
 │
-├── assets/                     # Assets embedded at compile time via include_bytes!()
+├── assets/                     # Loaded at runtime via AssetServer (audio is embedded via include_bytes!())
 │   ├── cards/
-│   │   ├── faces/{rank}_{suit}.png  # 52 individual card faces (120×168, generated by solitaire_assetgen)
-│   │   └── backs/back_0.png – back_4.png    # placeholder patterns
-│   ├── backgrounds/bg_0.png – bg_4.png      # placeholder textures
+│   │   ├── faces/{RANK}{SUIT}.png   # 52 card faces — xCards @2x artwork (LGPL-3.0)
+│   │   └── backs/back_0.png – back_4.png    # back_0 = xCards bicycle_blue; back_1–4 are generated patterns
+│   ├── backgrounds/bg_0.png – bg_4.png      # generated textures
 │   ├── fonts/main.ttf          # FiraMono-Medium (170K, OFL)
 │   └── audio/
 │       ├── card_deal.wav
@@ -144,7 +145,7 @@ Owns:
 - All Bevy UI screens (Home, Stats, Achievements, Settings, Profile)
 - Audio playback systems
 - Sync status display
-- Card, background, and font asset loading (embedded via `include_bytes!()` — no `AssetServer` dependency)
+- Card, background, and font asset loading via Bevy `AssetServer` (audio is the lone exception — embedded via `include_bytes!()` in `audio_plugin.rs`)
 
 ### `solitaire_server`
 **Dependencies:** `solitaire_sync`, `axum`, `sqlx`, `jsonwebtoken`, `bcrypt`, `tower-governor`, `tracing`, `tokio`, `dotenvy`.
@@ -235,11 +236,13 @@ Done
 
 ### Bevy Plugins
 
-| Plugin | Key | Responsibility |
+The "Shortcut" column lists optional keyboard accelerators. Every action in this table must also be reachable from a visible UI control (button, menu item, on-screen affordance) per the UI-first design principle in §1; the shortcut is a power-user convenience, not the sole entry point.
+
+| Plugin | Shortcut | Responsibility |
 |---|---|---|
 | `CardPlugin` | — | Card entity spawning, sprite management, drag-and-drop |
 | `TablePlugin` | — | Pile markers, background, layout calculation |
-| `FontPlugin` | — | Embeds FiraMono-Medium font at compile time; exposes `FontResource` handle |
+| `FontPlugin` | — | Loads FiraMono-Medium via `AssetServer` at startup; exposes `FontResource` handle |
 | `AnimationPlugin` | — | Slide, flip, win cascade, toast animations |
 | `FeedbackAnimPlugin` | — | Shake, settle, and deal-stagger animations |
 | `AutoCompletePlugin` | Enter | Executes auto-complete when the HUD badge is lit |
@@ -296,7 +299,7 @@ struct CardImageSet {
     backs: [Handle<Image>; 5],       // indexed by selected_card_back setting
 }
 
-// Project-wide font handle (FiraMono-Medium embedded at compile time)
+// Project-wide font handle (FiraMono-Medium loaded via AssetServer at startup)
 struct FontResource(Handle<Font>);
 
 // Pre-loaded background PNG handles
@@ -772,11 +775,13 @@ Audio systems listen for Bevy events and never block the game thread.
 
 ### Rendering approach
 
-Cards are Bevy `Sprite` entities with `Handle<Image>` from `CardImageSet`. Face-up cards use one of 52 individual face PNGs selected by `faces[suit][rank]` — rank and suit are baked into each image and no `Text2d` overlay is spawned. Face-down cards use `backs/back_N.png` indexed by `settings.selected_card_back`. `Text2d` labels are only used as a fallback when `CardImageSet` is absent (e.g. tests with `MinimalPlugins`). `CardImageSet` is populated at startup from `include_bytes!()` — no `AssetServer`.
+Cards are Bevy `Sprite` entities with `Handle<Image>` from `CardImageSet`. Face-up cards use one of 52 individual face PNGs selected by `faces[suit][rank]` — rank and suit are baked into each image and no `Text2d` overlay is spawned. Face-down cards use `backs/back_N.png` indexed by `settings.selected_card_back`. `Text2d` labels are only used as a fallback when `CardImageSet` is absent (e.g. tests with `MinimalPlugins`). `CardImageSet` is populated at startup by `card_plugin::load_card_images` via `AssetServer::load()`.
 
-Backgrounds are Bevy `Sprite` entities with `Handle<Image>` from `BackgroundImageSet`. `BackgroundImageSet` is populated at startup from `include_bytes!()`.
+Backgrounds are Bevy `Sprite` entities with `Handle<Image>` from `BackgroundImageSet`. `BackgroundImageSet` is populated at startup by `table_plugin::load_background_images` via `AssetServer::load()`.
 
-The font `FiraMono-Medium` is embedded via `include_bytes!()` at startup by `FontPlugin` and exposed as `FontResource` for use by all UI and text systems.
+The font `FiraMono-Medium` is loaded via `AssetServer::load("fonts/main.ttf")` at startup by `FontPlugin` and exposed as `FontResource` for use by all UI and text systems.
+
+All three loaders take `Option<Res<AssetServer>>` so they degrade cleanly under `MinimalPlugins` in tests: when the server is absent, `CardImageSet`/`BackgroundImageSet` are inserted with empty handle slots and the plugins fall back to `Text2d` rank+suit overlays and solid-colour board backgrounds. The `assets/` directory must ship alongside the binary.
 
 The `assets/` directory layout:
 
@@ -1004,5 +1009,5 @@ Using `axum::test` and an in-memory SQLite database:
 | `SyncProvider` trait, not `SyncBackend` match arms | `SyncPlugin` stays backend-agnostic and testable; new backends can be added without touching the plugin | 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 |
 | Dropped GPGS backend | Redundant with the self-hosted server; adds JNI complexity for no user-visible benefit on the target platforms | 2026-04-28 |
-| PNG assets embedded via `include_bytes!()` | Using `Image::from_buffer()` in startup systems rather than `AssetServer::load()` keeps the binary self-contained and eliminates runtime file-not-found errors | 2026-04-29 |
-| FiraMono-Medium font embedded via `include_bytes!()` | Exposed through `FontResource`; avoids runtime font loading errors on headless systems and ensures consistent text rendering across all platforms | 2026-04-29 |
+| Card, background, and font assets loaded via `AssetServer` | Reverses the earlier embed-via-`include_bytes!()` decision: PNGs and TTFs are loaded at runtime so artwork can be swapped (e.g. xCards @2x faces, alternate card backs, themed backgrounds) without a recompile, and binary size stays small. Loaders take `Option<Res<AssetServer>>` and fall back gracefully under `MinimalPlugins`. The `assets/` directory must ship alongside the binary. | 2026-04-29 |
+| Audio assets remain embedded via `include_bytes!()` | Audio files are small, change rarely, and the embedded path eliminates a class of runtime-load errors during gameplay; the asset-pipeline reversal does not extend to audio | 2026-04-29 |

CLAUDE.md

@@ -47,7 +47,9 @@ cargo clippy -p solitaire_core -- -D warnings
 
 - `solitaire_core` and `solitaire_sync` must never gain Bevy or network dependencies.
 - No `unwrap()` or `panic!()` in game logic. All state transitions return `Result<_, MoveError>`.
-- Audio assets are embedded at compile time using `include_bytes!()` in `audio_plugin.rs`. Cards and backgrounds are rendered procedurally (colored `Sprite` entities + text) — no image files are used and no `AssetServer` is needed.
+- Audio assets are embedded at compile time using `include_bytes!()` in `audio_plugin.rs`.
+- Card faces (52 PNGs in `assets/cards/faces/`), card backs (`assets/cards/backs/back_N.png`), board backgrounds (`assets/backgrounds/bg_N.png`), and the UI font (`assets/fonts/main.ttf`) are loaded at runtime via `AssetServer::load()` and stored as `Handle<Image>`/`Handle<Font>` in the `CardImageSet`, `BackgroundImageSet`, and `FontResource` resources. The `assets/` directory must ship alongside the binary.
+- Asset-loading systems take `Option<Res<AssetServer>>` so they degrade cleanly under `MinimalPlugins` (tests). When `CardImageSet` is absent, `card_plugin` falls back to a `Text2d` rank+suit overlay; when `BackgroundImageSet` is absent, the board falls back to a solid colour.
 - Atomic file writes only: write to `filename.json.tmp`, then `rename()`.
 - 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.
@@ -75,6 +77,7 @@ cargo clippy -p solitaire_core -- -D warnings
 - Resources own shared state. Events communicate between systems. Components own per-entity data.
 - All UI screens are built with Bevy UI (`bevy::ui`). Never mix UI layout and game logic in the same system.
 - Layout is recomputed on `WindowResized` — never assume a fixed window size.
+- **UI-first.** Every player-triggered action (new game, undo, draw, pause, open stats / settings / help / profile / leaderboard, switch mode, etc.) must be reachable from a visible UI control. Keyboard shortcuts are optional accelerators — never the sole entry point. New gameplay features ship with the UI control alongside the system that backs it; do not merge a feature that is keyboard-only.
 
 ---