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_data/src/solver.rs

@@ -93,7 +93,7 @@ fn solve_game_state(initial: &GameState, config: &SolverConfig) -> SolveOutcome
 
     // Preserve the historical payload contract: winnable verdicts always carry
     // a first move. An already-won state therefore returns no recommendation.
-    if initial.is_won {
+    if initial.is_won() {
         return SolveOutcome {
             result: SolverResult::Unwinnable,
             first_move: None,
@@ -101,7 +101,7 @@ fn solve_game_state(initial: &GameState, config: &SolverConfig) -> SolveOutcome
     }
 
     let solver_config = SessionConfig {
-        inner: KlondikeAdapter::config_for(initial.draw_mode, initial.take_from_foundation),
+        inner: KlondikeAdapter::config_for(initial.draw_mode(), initial.take_from_foundation),
         undo_penalty: 0,
         solve_moves_budget: config.move_budget,
         solve_states_budget: config.state_budget as u64,