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/input_plugin.rs

@@ -305,7 +305,7 @@ fn handle_keyboard_hint(
 
     let Some(ref g) = game else { return };
 
-    if g.0.is_won {
+    if g.0.is_won() {
         info_toast.write(InfoToastEvent(
             "Game won! Press N for a new game".to_string(),
         ));
@@ -1153,7 +1153,7 @@ fn card_position(
             y_offset -= layout.card_size.y * step;
         }
         Vec2::new(base.x, base.y + y_offset)
-    } else if matches!(pile, KlondikePile::Stock) && game.draw_mode == DrawMode::DrawThree {
+    } else if matches!(pile, KlondikePile::Stock) && game.draw_mode() == DrawMode::DrawThree {
         // In Draw-Three mode the top 3 waste cards are fanned in X to match
         // card_plugin::card_positions(). Hit-testing must use the same offsets
         // so clicking the visually rightmost (top) card actually registers.