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/resources.rs

@@ -6,7 +6,7 @@ use bevy::math::Vec2;
 use bevy::prelude::Resource;
 use chrono::{DateTime, Utc};
 use solitaire_core::game_state::GameState;
-use solitaire_core::pile::PileType;
+use klondike::KlondikePile;
 
 /// Wraps the currently active `GameState`. Single source of truth for the in-progress game.
 #[derive(Resource, Debug, Clone)]
@@ -29,7 +29,7 @@ pub struct DragState {
     /// IDs of the cards being dragged (bottom-to-top stacking order).
     pub cards: Vec<u32>,
     /// Pile the drag originated from.
-    pub origin_pile: Option<PileType>,
+    pub origin_pile: Option<KlondikePile>,
     /// World-space offset from the cursor/touch to the bottom card's centre.
     pub cursor_offset: Vec2,
     /// Z coordinate used for the dragged cards.