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_core/src/pile.rs

@@ -1,33 +1,18 @@
 use crate::card::{Card, Suit};
-use serde::{Deserialize, Serialize};
-
-/// Identifies which pile on the board a set of cards belongs to.
-#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
-pub enum PileType {
-    /// The face-down draw pile.
-    Stock,
-    /// The face-up discard pile drawn to.
-    Waste,
-    /// One of the four foundation slots (0..=3). The claimed suit, if any,
-    /// is derived from the bottom card of the pile (always an Ace by
-    /// construction).
-    Foundation(u8),
-    /// One of the seven tableau columns (0–6).
-    Tableau(usize),
-}
+use klondike::KlondikePile;
 
 /// A named collection of cards in a specific board position.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Pile {
-    /// Which pile this is (Stock, Waste, Foundation slot, or Tableau column).
-    pub pile_type: PileType,
+    /// Which logical Klondike pile this is.
+    pub pile_type: KlondikePile,
     /// Cards in the pile, bottom-to-top stacking order. Last element is the top card.
     pub cards: Vec<Card>,
 }
 
 impl Pile {
     /// Creates a new empty pile of the given type.
-    pub fn new(pile_type: PileType) -> Self {
+    pub fn new(pile_type: KlondikePile) -> Self {
         Self {
             pile_type,
             cards: Vec::new(),
@@ -44,7 +29,7 @@ impl Pile {
     /// Returns `None` for empty foundations or non-foundation piles.
     pub fn claimed_suit(&self) -> Option<Suit> {
         match self.pile_type {
-            PileType::Foundation(_) => self.cards.first().map(|c| c.suit),
+            KlondikePile::Foundation(_) => self.cards.first().map(|c| c.suit),
             _ => None,
         }
     }
@@ -57,13 +42,13 @@ mod tests {
 
     #[test]
     fn new_pile_is_empty() {
-        let pile = Pile::new(PileType::Stock);
+        let pile = Pile::new(KlondikePile::Stock);
         assert!(pile.cards.is_empty());
     }
 
     #[test]
     fn pile_top_returns_last_card() {
-        let mut pile = Pile::new(PileType::Waste);
+        let mut pile = Pile::new(KlondikePile::Stock);
         pile.cards.push(Card {
             id: 0,
             suit: Suit::Hearts,
@@ -81,29 +66,19 @@ mod tests {
 
     #[test]
     fn pile_top_on_empty_is_none() {
-        let pile = Pile::new(PileType::Waste);
+        let pile = Pile::new(KlondikePile::Stock);
         assert!(pile.top().is_none());
     }
 
-    #[test]
-    fn pile_type_foundation_uses_slot_index() {
-        assert_ne!(PileType::Foundation(0), PileType::Foundation(3));
-    }
-
-    #[test]
-    fn pile_type_tableau_uses_index() {
-        assert_ne!(PileType::Tableau(0), PileType::Tableau(6));
-    }
-
     #[test]
     fn claimed_suit_is_none_for_empty_foundation() {
-        let pile = Pile::new(PileType::Foundation(0));
+        let pile = Pile::new(KlondikePile::Foundation(klondike::Foundation::Foundation1));
         assert!(pile.claimed_suit().is_none());
     }
 
     #[test]
     fn claimed_suit_is_none_for_non_foundation() {
-        let mut pile = Pile::new(PileType::Tableau(0));
+        let mut pile = Pile::new(KlondikePile::Tableau(klondike::Tableau::Tableau1));
         pile.cards.push(Card {
             id: 0,
             suit: Suit::Hearts,
@@ -115,7 +90,7 @@ mod tests {
 
     #[test]
     fn claimed_suit_returns_bottom_card_suit() {
-        let mut pile = Pile::new(PileType::Foundation(2));
+        let mut pile = Pile::new(KlondikePile::Foundation(klondike::Foundation::Foundation3));
         pile.cards.push(Card {
             id: 0,
             suit: Suit::Hearts,