refactor: migrate PileType → KlondikePile across core/wasm/engine

- Replace PileType with typed KlondikePile (Foundation/Tableau variants)
  throughout solitaire_core, solitaire_wasm, and solitaire_engine;
  ReplayMove now uses SavedKlondikePile for serialisation stability
- Split replay_overlay.rs into replay_overlay/ module (mod, format,
  input, update, tests) for maintainability
- Add klondike dep to solitaire_engine and solitaire_data Cargo.toml
- Add TestPileState infrastructure to game_state.rs for engine unit tests
- Rebuild solitaire_wasm pkg (js + wasm artefacts updated)

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

solitaire_engine/src/events.rs

@@ -1,9 +1,9 @@
 //! Cross-system events used by the engine's plugins.
 
 use bevy::prelude::Message;
+use klondike::KlondikePile;
 use solitaire_core::card::Suit;
 use solitaire_core::game_state::GameMode;
-use solitaire_core::pile::PileType;
 use solitaire_data::AchievementRecord;
 use solitaire_sync::SyncResponse;
 
@@ -11,8 +11,8 @@ use solitaire_sync::SyncResponse;
 /// consumed by `GamePlugin`.
 #[derive(Message, Debug, Clone)]
 pub struct MoveRequestEvent {
-    pub from: PileType,
-    pub to: PileType,
+    pub from: KlondikePile,
+    pub to: KlondikePile,
     pub count: usize,
 }
 
@@ -49,8 +49,8 @@ pub struct StateChangedEvent;
 /// `card_invalid.wav` SFX. Not fired for drops in empty space.
 #[derive(Message, Debug, Clone)]
 pub struct MoveRejectedEvent {
-    pub from: PileType,
-    pub to: PileType,
+    pub from: KlondikePile,
+    pub to: KlondikePile,
     pub count: usize,
 }
 
@@ -302,5 +302,5 @@ pub struct HintVisualEvent {
     /// The `Card::id` of the source card to be highlighted.
     pub source_card_id: u32,
     /// The destination pile whose `PileMarker` should be tinted gold.
-    pub dest_pile: solitaire_core::pile::PileType,
+    pub dest_pile: KlondikePile,
 }