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/challenge_plugin.rs

@@ -117,7 +117,7 @@ mod tests {
     use crate::game_plugin::GamePlugin;
     use crate::progress_plugin::ProgressPlugin;
     use crate::table_plugin::TablePlugin;
-    use solitaire_core::{DrawMode, game_state::GameState};
+    use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     fn headless_app() -> App {
         let mut app = App::new();
@@ -135,7 +135,7 @@ mod tests {
     fn challenge_win_advances_index() {
         let mut app = headless_app();
         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 {
             score: 500,
@@ -224,7 +224,7 @@ mod tests {
             .0
             .challenge_index = 2;
         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 {
             score: 500,