refactor(core): integrate card_game/klondike deps cleanly

Wire card_game 0.4.0 and klondike 0.3.0 as workspace deps in
solitaire_core and clean the integration seam across five areas:

- Move From<card_game::Suit/Rank> bridge impls out of card.rs and into
  klondike_adapter.rs so the product-type module is upstream-dep-free
- Add `use crate::card` alias to adapter; rename card_from_kl parameter
  to avoid shadowing; correct score_for_undo doc (it is Ferrous policy,
  not an upstream default — the solver explicitly passes undo_penalty=0)
- Mark Pile as a read-only projection / data-transfer type in its doc
  comment so game logic isn't accidentally routed through it
- Add GameState::session() read accessor exposing the underlying
  Session<Klondike> for replay history and solver use by external crates;
  update solver.rs to use the accessor instead of the pub(crate) field
- Re-export Foundation, Klondike, KlondikePile, Session, Tableau from
  solitaire_core::lib so downstream crates (engine, wasm) can import
  from one place without a direct klondike/card_game dep
- Add proptest property tests: card conservation (52 unique IDs always
  present), deal determinism, undo pile-layout invariant, legal moves
  always succeed

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

solitaire_core/src/proptest_tests.rs

@@ -0,0 +1,224 @@
+use klondike::{Foundation, KlondikePile, Tableau};
+use proptest::prelude::*;
+
+use crate::game_state::{DrawMode, GameState};
+
+// ---------------------------------------------------------------------------
+// Shared helpers
+// ---------------------------------------------------------------------------
+
+/// Collect all card IDs across every pile in a fixed traversal order:
+/// stock → waste → foundations 1–4 → tableaux 1–7.
+///
+/// The order is deterministic for a given game state, so two calls on
+/// equivalent states produce identical Vec outputs — the right fingerprint
+/// for undo-reversibility checks.
+fn all_card_ids(game: &GameState) -> Vec<u32> {
+    let foundations = [
+        Foundation::Foundation1,
+        Foundation::Foundation2,
+        Foundation::Foundation3,
+        Foundation::Foundation4,
+    ];
+    let tableaux = [
+        Tableau::Tableau1,
+        Tableau::Tableau2,
+        Tableau::Tableau3,
+        Tableau::Tableau4,
+        Tableau::Tableau5,
+        Tableau::Tableau6,
+        Tableau::Tableau7,
+    ];
+
+    let mut ids: Vec<u32> = game.stock_cards().iter().map(|c| c.id).collect();
+    ids.extend(game.waste_cards().iter().map(|c| c.id));
+    for f in &foundations {
+        ids.extend(
+            game.pile(KlondikePile::Foundation(*f))
+                .iter()
+                .map(|c| c.id),
+        );
+    }
+    for t in &tableaux {
+        ids.extend(game.pile(KlondikePile::Tableau(*t)).iter().map(|c| c.id));
+    }
+    ids
+}
+
+fn draw_mode_strategy() -> impl Strategy<Value = DrawMode> {
+    prop_oneof![Just(DrawMode::DrawOne), Just(DrawMode::DrawThree)]
+}
+
+/// Apply a sequence of random actions to a game, silently ignoring errors.
+///
+/// Each action is `(draw_flag, move_index)`:
+/// - `draw_flag = true`  → call `game.draw()`
+/// - `draw_flag = false` → pick the `move_index % len`th legal move from
+///   `possible_instructions()` and execute it.
+///
+/// `possible_instructions()` may return `(Stock, Stock, 1)` for the
+/// RotateStock / draw action. `move_cards(Stock, Stock, 1)` is rejected by
+/// the `from == to` guard, so those are dispatched to `game.draw()`.
+fn apply_random_actions(game: &mut GameState, actions: &[(bool, usize)]) {
+    for &(do_draw, idx) in actions {
+        if do_draw {
+            let _ = game.draw();
+        } else {
+            let instructions = game.possible_instructions();
+            if instructions.is_empty() {
+                continue;
+            }
+            let (from, to, count) = instructions[idx % instructions.len()];
+            if from == to {
+                let _ = game.draw();
+            } else {
+                let _ = game.move_cards(from, to, count);
+            }
+        }
+    }
+}
+
+/// Apply one move from `possible_instructions()` (or a draw if no move is
+/// available), using `move_idx` to select among the legal options.
+/// Returns `true` when a move was successfully applied.
+fn apply_one_move(game: &mut GameState, move_idx: usize) -> bool {
+    if game.is_won {
+        return false;
+    }
+    let instructions = game.possible_instructions();
+    if instructions.is_empty() {
+        return game.draw().is_ok();
+    }
+    let (from, to, count) = instructions[move_idx % instructions.len()];
+    if from == to {
+        game.draw().is_ok()
+    } else {
+        game.move_cards(from, to, count).is_ok()
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Properties
+// ---------------------------------------------------------------------------
+
+proptest! {
+    /// All 52 card IDs must be present exactly once across every pile after
+    /// any reachable sequence of draw + move_cards actions.
+    ///
+    /// Catches two bug classes at once:
+    /// - Card loss (fewer than 52 unique IDs after the sequence).
+    /// - Card duplication (52 total but deduplication reduces the set).
+    #[test]
+    fn all_52_cards_always_present(
+        seed in any::<u64>(),
+        draw_mode in draw_mode_strategy(),
+        actions in prop::collection::vec((any::<bool>(), 0usize..200), 0..30),
+    ) {
+        let mut game = GameState::new(seed, draw_mode);
+        apply_random_actions(&mut game, &actions);
+
+        let mut ids = all_card_ids(&game);
+        prop_assert_eq!(ids.len(), 52, "card count ≠ 52 (got {})", ids.len());
+        ids.sort_unstable();
+        ids.dedup();
+        prop_assert_eq!(
+            ids.len(), 52,
+            "duplicate card IDs found after dedup — a card was cloned"
+        );
+    }
+
+    /// `GameState::new(seed, draw_mode)` must be deterministic: two calls
+    /// with the same arguments must produce identical initial pile layouts.
+    ///
+    /// Pins that the deal is seeded from `seed` alone and not from any
+    /// implicit source like wall-clock time or global state.
+    #[test]
+    fn deal_is_deterministic(
+        seed in any::<u64>(),
+        draw_mode in draw_mode_strategy(),
+    ) {
+        let a = GameState::new(seed, draw_mode);
+        let b = GameState::new(seed, draw_mode);
+        prop_assert_eq!(
+            all_card_ids(&a),
+            all_card_ids(&b),
+            "same seed + draw_mode produced different deals",
+        );
+    }
+
+    /// After applying any single legal move and immediately undoing it, the
+    /// pile layout and move_count must be identical to their pre-move values.
+    ///
+    /// `setup_actions` drives the game to an arbitrary mid-game position;
+    /// `move_idx` selects which legal move to apply and then undo.
+    ///
+    /// The score is intentionally excluded: `undo()` applies a −15 penalty
+    /// that is by design, not a regression.
+    #[test]
+    fn undo_restores_pile_layout_and_move_count(
+        seed in any::<u64>(),
+        draw_mode in draw_mode_strategy(),
+        setup_actions in prop::collection::vec((any::<bool>(), 0usize..200), 0..20),
+        move_idx in 0usize..200,
+    ) {
+        let mut game = GameState::new(seed, draw_mode);
+        apply_random_actions(&mut game, &setup_actions);
+
+        // Snapshot the state before the move.
+        let before_ids = all_card_ids(&game);
+        let before_move_count = game.move_count;
+
+        // Apply one move.
+        if !apply_one_move(&mut game, move_idx) || game.is_won {
+            return Ok(()); // nothing to undo
+        }
+
+        // Undo and verify.
+        prop_assert!(
+            game.undo().is_ok(),
+            "undo must succeed immediately after a successful move",
+        );
+        prop_assert_eq!(
+            all_card_ids(&game),
+            before_ids,
+            "pile layout after undo differs from the pre-move snapshot",
+        );
+        prop_assert_eq!(
+            game.move_count,
+            before_move_count,
+            "move_count after undo must equal the pre-move value",
+        );
+    }
+
+    /// Every move returned by `possible_instructions()` must succeed when
+    /// applied via `move_cards()`.
+    ///
+    /// `possible_instructions()` and `move_cards()` both validate moves
+    /// through the same upstream rule engine. This property ensures no
+    /// drift has opened up between what the engine reports as legal and
+    /// what it actually accepts.
+    #[test]
+    fn legal_moves_always_succeed(
+        seed in any::<u64>(),
+        draw_mode in draw_mode_strategy(),
+        setup_actions in prop::collection::vec((any::<bool>(), 0usize..200), 0..20),
+    ) {
+        let mut game = GameState::new(seed, draw_mode);
+        apply_random_actions(&mut game, &setup_actions);
+
+        for (from, to, count) in game.possible_instructions() {
+            // Clone so each move is tried from the same starting state.
+            let mut trial = game.clone();
+            let result = if from == to {
+                trial.draw()
+            } else {
+                trial.move_cards(from, to, count)
+            };
+            prop_assert!(
+                result.is_ok(),
+                "possible_instructions() reported ({from:?} → {to:?} ×{count}) \
+                 as legal but the call returned Err: {result:?}",
+            );
+        }
+    }
+}