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/hud_plugin.rs

@@ -8,9 +8,9 @@
 
 use bevy::prelude::*;
 use bevy::window::WindowResized;
+use klondike::{Foundation, KlondikePile, Tableau};
 use solitaire_core::card::Suit;
 use solitaire_core::game_state::{DrawMode, GameMode};
-use solitaire_core::pile::PileType;
 
 use crate::auto_complete_plugin::AutoCompleteState;
 use crate::avatar_plugin::AvatarResource;
@@ -2316,7 +2316,7 @@ fn update_hud(
                 // Hide when not in Draw-Three or after the game is won.
                 String::new()
             } else {
-                let stock_len = g.piles[&solitaire_core::pile::PileType::Stock].cards.len();
+                let stock_len = g.stock_cards().len();
                 let next_draw = stock_len.min(3);
                 format!("Cycle: {next_draw}/3")
             };
@@ -2380,15 +2380,14 @@ fn update_selection_hud(
     let Ok(mut t) = q.single_mut() else { return };
     let label = match selection.as_deref().and_then(|s| s.selected_pile.as_ref()) {
         None => String::new(),
-        Some(PileType::Waste) => "▶ Waste".to_string(),
-        Some(PileType::Stock) => "▶ Stock".to_string(),
-        Some(PileType::Foundation(slot)) => match game.as_deref() {
+        Some(KlondikePile::Stock) => "▶ Waste".to_string(),
+        Some(KlondikePile::Foundation(slot)) => match game.as_deref() {
             Some(g) => foundation_selection_label(*slot, &g.0),
             // No game resource means we can't probe claimed_suit; show the
             // slot-based placeholder so the HUD still surfaces the selection.
-            None => format!("▶ Foundation {}", slot + 1),
+            None => format!("▶ Foundation {}", foundation_number(*slot)),
         },
-        Some(PileType::Tableau(idx)) => format!("▶ Column {}", idx + 1),
+        Some(KlondikePile::Tableau(idx)) => format!("▶ Column {}", tableau_number(*idx)),
     };
     **t = label;
 }
@@ -2398,11 +2397,11 @@ fn update_selection_hud(
 /// When the slot has a claimed suit (any card has landed) the announcement is
 /// "▶ {Suit} Foundation"; while the slot is empty it falls back to a
 /// "▶ Foundation N" placeholder labelled by the 1-based slot index.
-fn foundation_selection_label(slot: u8, game: &solitaire_core::game_state::GameState) -> String {
+fn foundation_selection_label(slot: Foundation, game: &solitaire_core::game_state::GameState) -> String {
     let claimed = game
-        .piles
-        .get(&PileType::Foundation(slot))
-        .and_then(|p| p.claimed_suit());
+        .pile(KlondikePile::Foundation(slot))
+        .first()
+        .map(|c| c.suit);
     match claimed {
         Some(suit) => {
             let s = match suit {
@@ -2413,7 +2412,28 @@ fn foundation_selection_label(slot: u8, game: &solitaire_core::game_state::GameS
             };
             format!("▶ {s} Foundation")
         }
-        None => format!("▶ Foundation {}", slot + 1),
+        None => format!("▶ Foundation {}", foundation_number(slot)),
+    }
+}
+
+const fn foundation_number(foundation: Foundation) -> u8 {
+    match foundation {
+        Foundation::Foundation1 => 1,
+        Foundation::Foundation2 => 2,
+        Foundation::Foundation3 => 3,
+        Foundation::Foundation4 => 4,
+    }
+}
+
+const fn tableau_number(tableau: Tableau) -> u8 {
+    match tableau {
+        Tableau::Tableau1 => 1,
+        Tableau::Tableau2 => 2,
+        Tableau::Tableau3 => 3,
+        Tableau::Tableau4 => 4,
+        Tableau::Tableau5 => 5,
+        Tableau::Tableau6 => 6,
+        Tableau::Tableau7 => 7,
     }
 }