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/stats_plugin.rs

@@ -1327,7 +1327,7 @@ mod tests {
         app.world_mut()
             .resource_mut::<crate::resources::GameStateResource>()
             .0
-            .set_test_draw_mode(solitaire_core::DrawMode::DrawThree);
+            .set_test_draw_mode(solitaire_core::DrawStockConfig::DrawThree);
 
         app.world_mut().write_message(GameWonEvent {
             score: 500,
@@ -1952,7 +1952,7 @@ mod tests {
         let date = chrono::NaiveDate::from_ymd_opt(2026, 5, 8).expect("valid date");
         let mut r = solitaire_data::Replay::new(
             1,
-            solitaire_core::DrawMode::DrawOne,
+            solitaire_core::DrawStockConfig::DrawOne,
             solitaire_core::game_state::GameMode::Classic,
             time_seconds,
             0,