refactor(core): derive draw_mode/is_won/move_count/is_auto_completable from session

Remove the draw_mode, move_count, is_won, and is_auto_completable fields
from GameState; they are now &self methods deriving from the underlying
card_game session (draw_mode from session config, move_count from history
length, is_won/is_auto_completable from check_win/check_auto_complete).

Tests previously fabricated these via direct field writes, which is no
longer possible. Add gated test-support overrides on TestPileState
(won/auto_completable/move_count) plus setters set_test_won,
set_test_auto_completable, set_test_move_count, and set_test_draw_mode
(re-deals the seed). All compiled out in production builds.

Fix the field->method ripple across solitaire_data, solitaire_wasm, and
solitaire_engine. Add a test-support dev-dependency to solitaire_data for
the won-game storage test.

cargo test --workspace and cargo clippy --workspace -- -D warnings pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_engine/src/auto_complete_plugin.rs

@@ -76,14 +76,14 @@ fn detect_auto_complete(
     }
     changed.clear();
 
-    if game.0.is_won {
+    if game.0.is_won() {
         state.active = false;
         return;
     }
-    if game.0.is_auto_completable && !state.active {
+    if game.0.is_auto_completable() && !state.active {
         state.active = true;
         state.cooldown = AUTO_COMPLETE_INITIAL_DELAY;
-    } else if !game.0.is_auto_completable && state.active {
+    } else if !game.0.is_auto_completable() && state.active {
         // `is_auto_completable` only becomes false after an explicit undo
         // (which puts a card back on the tableau or re-fills the stock/waste)
         // or a new-game reset — never as a transient gap during a normal
@@ -209,7 +209,7 @@ mod tests {
             Tableau::Tableau1,
             vec![solitaire_core::card::Card::new(Deck::Deck1, Suit::Clubs, Rank::Ace)],
         );
-        g.is_auto_completable = true;
+        g.set_test_auto_completable(true);
         let expected = (
             KlondikePile::Tableau(Tableau::Tableau1),
             KlondikePile::Foundation(Foundation::Foundation1),
@@ -228,7 +228,7 @@ mod tests {
     fn detect_activates_when_auto_completable() {
         let mut app = headless_app();
         let mut g = GameState::new(42, DrawMode::DrawOne);
-        g.is_auto_completable = true;
+        g.set_test_auto_completable(true);
         app.world_mut().resource_mut::<GameStateResource>().0 = g;
         app.world_mut().write_message(StateChangedEvent);
         app.update();
@@ -263,7 +263,7 @@ mod tests {
         let mut app = headless_app();
         // Inject a won game state — active should not be set.
         let (mut gs, _) = seeded_state_with_auto_move();
-        gs.is_won = true;
+        gs.set_test_won(true);
         app.world_mut().resource_mut::<GameStateResource>().0 = gs;
         app.world_mut().write_message(StateChangedEvent);
         app.update();