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/card_plugin.rs

@@ -734,7 +734,7 @@ fn sync_cards(
     // Without this, the buffer sits at waste_base uncovered during the animation
     // and its rank/suit peek behind the incoming card.
     let waste_buffer_id: Option<Card> = {
-        let visible = match game.draw_mode {
+        let visible = match game.draw_mode() {
             DrawMode::DrawOne => 1_usize,
             DrawMode::DrawThree => 3_usize,
         };
@@ -903,7 +903,7 @@ fn card_positions(game: &GameState, layout: &Layout) -> Vec<((Card, bool), Vec2,
         // while new cards animate in from the stock. Draw-One shows 1; Draw-Three
         // shows up to 3 fanned in X (matching the standard Klondike presentation).
         let render_start = if is_waste {
-            let visible = match game.draw_mode {
+            let visible = match game.draw_mode() {
                 DrawMode::DrawOne => 1_usize,
                 DrawMode::DrawThree => 3_usize,
             };
@@ -918,7 +918,7 @@ fn card_positions(game: &GameState, layout: &Layout) -> Vec<((Card, bool), Vec2,
         let mut y_offset = 0.0_f32;
         let rendered_len = cards[render_start..].len();
         for (slot, (card, face_up)) in cards[render_start..].iter().enumerate() {
-            let x_offset = if is_waste && matches!(game.draw_mode, DrawMode::DrawThree) {
+            let x_offset = if is_waste && matches!(game.draw_mode(), DrawMode::DrawThree) {
                 // When len > visible, slot 0 is a hidden buffer card kept at
                 // x=0 to prevent a flash during the draw tween. When len ≤
                 // visible (small pile), every card is visible and should fan