refactor: replace local DrawMode with upstream klondike::DrawStockConfig (#82)

DrawMode was a 1:1 mirror of klondike::DrawStockConfig (DrawOne/DrawThree).
Delete it and use the upstream type everywhere; re-export DrawStockConfig from
solitaire_core. config_for assigns draw_stock directly and draw_mode() returns
session.config().inner.draw_stock.

Serde is unchanged — DrawStockConfig serialises to the same "DrawOne"/"DrawThree"
named variants, so persisted game_state.json / replay JSON stay byte-compatible
(no migration). Field/method/variable names containing draw_mode are unchanged.

35 files, mechanical type swap across all crates. Implemented via a multi-agent
workflow (core → per-crate consumers → verify). cargo test --workspace and
clippy --workspace --all-targets -- -D warnings green.

Closes #82

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_engine/src/win_summary_plugin.rs

@@ -1205,7 +1205,7 @@ mod tests {
             .insert_resource(StatsResource(StatsSnapshot::default()))
             .insert_resource(GameStateResource(GameState::new(
                 0,
-                solitaire_core::DrawMode::DrawOne,
+                solitaire_core::DrawStockConfig::DrawOne,
             )))
             .insert_resource(ProgressResource(PlayerProgress::default()));
         app.update();
@@ -1534,9 +1534,9 @@ mod tests {
             .challenge_index = 4;
         // Switch game mode to Challenge.
         {
-            use solitaire_core::DrawMode;
+            use solitaire_core::DrawStockConfig;
             app.world_mut().resource_mut::<GameStateResource>().0 =
-                GameState::new_with_mode(1, DrawMode::DrawOne, GameMode::Challenge);
+                GameState::new_with_mode(1, DrawStockConfig::DrawOne, GameMode::Challenge);
         }
 
         app.world_mut().write_message(GameWonEvent {
@@ -1580,13 +1580,13 @@ mod tests {
     /// mode-multiplier rows.
     #[test]
     fn cache_win_data_captures_undo_count_and_mode() {
-        use solitaire_core::DrawMode;
+        use solitaire_core::DrawStockConfig;
 
         let mut app = make_app();
         // Set up a Zen-mode game with 2 undos used.
         {
             let mut game = app.world_mut().resource_mut::<GameStateResource>();
-            game.0 = GameState::new_with_mode(7, DrawMode::DrawOne, GameMode::Zen);
+            game.0 = GameState::new_with_mode(7, DrawStockConfig::DrawOne, GameMode::Zen);
             game.0.force_test_undos(2);
         }