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/feedback_anim_plugin.rs

@@ -43,7 +43,7 @@ use std::hash::{Hash, Hasher};
 
 use bevy::prelude::*;
 use bevy::window::RequestRedraw;
-use solitaire_core::pile::PileType;
+use klondike::{Foundation, KlondikePile};
 use solitaire_data::AnimSpeed;
 
 use crate::animation_plugin::CardAnim;
@@ -246,10 +246,8 @@ fn start_shake_anim(
         }
         let dest_pile = &ev.to;
         // Collect the card ids that belong to the destination pile.
-        let Some(pile) = game.0.piles.get(dest_pile) else {
-            continue;
-        };
-        let dest_card_ids: Vec<u32> = pile.cards.iter().map(|c| c.id).collect();
+        let dest_cards = pile_cards(&game.0, dest_pile);
+        let dest_card_ids: Vec<u32> = dest_cards.iter().map(|c| c.id).collect();
 
         if dest_card_ids.is_empty() {
             continue;
@@ -319,19 +317,19 @@ fn start_settle_anim(
     let mut bounce_ids: Vec<u32> = Vec::new();
 
     for ev in moves.read() {
-        if let Some(pile) = game.0.piles.get(&ev.to) {
+        let pile = pile_cards(&game.0, &ev.to);
+        if !pile.is_empty() {
             // The moved cards land on top — take the last `count` ids.
-            let n = ev.count.min(pile.cards.len());
+            let n = ev.count.min(pile.len());
             if n > 0 {
-                let start = pile.cards.len() - n;
-                bounce_ids.extend(pile.cards[start..].iter().map(|c| c.id));
+                let start = pile.len() - n;
+                bounce_ids.extend(pile[start..].iter().map(|c| c.id));
             }
         }
     }
 
     if draws.read().next().is_some()
-        && let Some(pile) = game.0.piles.get(&PileType::Waste)
-        && let Some(top) = pile.cards.last()
+        && let Some(top) = game.0.waste_cards().last()
     {
         bounce_ids.push(top.id);
     }
@@ -399,7 +397,7 @@ fn start_deal_anim(
         return;
     }
     let Some(layout) = layout else { return };
-    let Some(&stock_pos) = layout.0.pile_positions.get(&PileType::Stock) else {
+    let Some(&stock_pos) = layout.0.pile_positions.get(&KlondikePile::Stock) else {
         return;
     };
     let stock_start = Vec3::new(stock_pos.x, stock_pos.y, 0.0);
@@ -520,15 +518,13 @@ fn start_foundation_flourish(
         if reduce_motion {
             continue;
         }
-        let pile_type = PileType::Foundation(ev.slot);
+        let Some(foundation) = foundation_from_slot(ev.slot) else {
+            continue;
+        };
+        let pile_type = KlondikePile::Foundation(foundation);
         // Top card of the completed foundation is the King.
-        let Some(king_id) = game
-            .0
-            .piles
-            .get(&pile_type)
-            .and_then(|p| p.cards.last())
-            .map(|c| c.id)
-        else {
+        let cards = game.0.pile(pile_type);
+        let Some(king_id) = cards.last().map(|c| c.id) else {
             continue;
         };
 
@@ -634,6 +630,26 @@ fn lerp_color(from: Color, to: Color, t: f32) -> Color {
     )
 }
 
+fn pile_cards(
+    game: &solitaire_core::game_state::GameState,
+    pile: &KlondikePile,
+) -> Vec<solitaire_core::card::Card> {
+    match pile {
+        KlondikePile::Stock => game.waste_cards(),
+        _ => game.pile(*pile),
+    }
+}
+
+fn foundation_from_slot(slot: u8) -> Option<Foundation> {
+    match slot {
+        0 => Some(Foundation::Foundation1),
+        1 => Some(Foundation::Foundation2),
+        2 => Some(Foundation::Foundation3),
+        3 => Some(Foundation::Foundation4),
+        _ => None,
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Unit tests (pure functions only — no Bevy world required)
 // ---------------------------------------------------------------------------
@@ -834,6 +850,7 @@ mod tests {
     fn shake_anim_skipped_under_reduce_motion() {
         use bevy::ecs::message::Messages;
         use solitaire_core::game_state::{DrawMode, GameState};
+        use klondike::Tableau;
         use solitaire_data::Settings;
 
         let mut app = App::new();
@@ -847,14 +864,13 @@ mod tests {
         app.update();
 
         // Pick a card from Tableau(0) so the event refers to a real pile.
-        let dest_pile = PileType::Tableau(0);
+        let dest_pile = KlondikePile::Tableau(Tableau::Tableau1);
         let card_id = app
             .world()
             .resource::<GameStateResource>()
             .0
-            .piles
-            .get(&dest_pile)
-            .and_then(|p| p.cards.last())
+            .pile(dest_pile)
+            .last()
             .map(|c| c.id)
             .expect("Tableau(0) should have at least one card in a fresh game");
 
@@ -866,7 +882,7 @@ mod tests {
         app.world_mut()
             .resource_mut::<Messages<MoveRejectedEvent>>()
             .write(MoveRejectedEvent {
-                from: PileType::Stock,
+                from: KlondikePile::Stock,
                 to: dest_pile,
                 count: 1,
             });