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/pause_plugin.rs

@@ -340,7 +340,7 @@ fn handle_forfeit_request(
     if !forfeit_screens.is_empty() {
         return;
     }
-    let game_in_progress = game.as_ref().is_some_and(|g| !g.0.is_won);
+    let game_in_progress = game.as_ref().is_some_and(|g| !g.0.is_won());
     if !game_in_progress {
         toast.write(InfoToastEvent("No game to forfeit".to_string()));
         return;
@@ -1025,7 +1025,7 @@ mod tests {
         app.add_plugins(MinimalPlugins).add_plugins(PausePlugin);
         app.init_resource::<ButtonInput<KeyCode>>();
         let mut game = GameState::new(1, DrawMode::DrawOne);
-        game.is_won = true;
+        game.set_test_won(true);
         app.insert_resource(GameStateResource(game));
         app.update();