docs(core,data): complete Phases 0–2 of in-place card_game rewrite

Phase 0 – doc fixes (docs/card-game-integration.md):
- Correct stale "no serde" claim: upstream has serde at rev 99b49e62
- Correct take_from_foundation default description (Allowed, not Disallowed)
- Document schema v3→v4 migration and AnyInstruction strategy

Phase 1 – delegate check_win / check_auto_complete to upstream:
- Proptests verify semantic agreement with is_win() / is_win_trivial()
  across 256 random states before delegation

Phase 2 – schema v4 with v3 auto-migration:
- SavedInstruction mirror types kept as legacy compat module (needed by
  solitaire_data::ReplayMove and solitaire_wasm replay layer)
- klondike_adapter.rs: add comprehensive legacy-purpose doc comment
- proptest_tests.rs: add check_auto_complete/check_win semantic proofs
- storage.rs: rename round-trip test to v4, add v3-migrates-to-v4 test

Also track the rewrite plan (docs/in-place-card-game-rewrite-plan.md).

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

solitaire_core/src/klondike_adapter.rs

@@ -223,17 +223,24 @@ pub fn card_from_kl(kl_card: &KlCard) -> card::Card {
     }
 }
 
-// ── Serde newtypes for KlondikeInstruction (Step 7) ──────────────────────────
+// ── Legacy serde mirror types (kept for backward compatibility) ───────────────
 //
-// `klondike::KlondikeInstruction` (and its sub-types) do not derive
-// `Serialize` / `Deserialize`.  These mirror types carry `#[serde]` so that
-// the session instruction history can be persisted and reconstructed without
-// upstream changes.
+// These types were introduced when upstream `klondike` had no serde feature.
+// At rev 99b49e62, upstream provides full serde support, and `GameState`
+// serialises `saved_moves` directly as `Vec<KlondikeInstruction>` (schema v4).
 //
-// Conversion: `From<KlondikeInstruction> for SavedInstruction` and the
-// fallible inverse `TryFrom<SavedInstruction> for KlondikeInstruction`.
-// Invalid numeric values (out-of-range u8 for tableau/foundation/skip) yield
-// `InvalidSavedInstruction`.
+// The mirror types are retained for three reasons:
+//   1. Schema v3 migration: `AnyInstruction` in `game_state.rs` uses
+//      `TryFrom<SavedInstruction> for KlondikeInstruction` to parse old save
+//      files with u8 indices and replay them.
+//   2. `solitaire_data::ReplayMove` uses `SavedKlondikePile` as its serde
+//      type; changing it would break the on-disk replay format (schema v2).
+//   3. `solitaire_wasm` mirrors `ReplayMove` using the same types so that
+//      replay JSON is cross-compatible between the desktop and browser builds.
+//
+// These types should not be used for new serialisation concerns.  If the
+// ReplayMove format is ever bumped to a new schema, migrate those callers to
+// `KlondikePile` / `KlondikePileStack` and the types here can then be deleted.
 
 /// A `Serialize` + `Deserialize` mirror of [`klondike::Tableau`] (0 = Tableau1 … 6 = Tableau7).
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]