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/cursor_plugin.rs

@@ -437,7 +437,7 @@ fn tableau_or_stack_pos(
             base.x,
             base.y - layout.card_size.y * layout.tableau_fan_frac * (index as f32),
         )
-    } else if matches!(pile, KlondikePile::Stock) && game.draw_mode == DrawMode::DrawThree {
+    } else if matches!(pile, KlondikePile::Stock) && game.draw_mode() == DrawMode::DrawThree {
         let pile_len = game.waste_cards().len();
         let visible_start = pile_len.saturating_sub(3);
         let slot = index.saturating_sub(visible_start) as f32;