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/selection_plugin.rs

@@ -935,7 +935,7 @@ mod tests {
 
     use bevy::ecs::message::Messages;
     use solitaire_core::card::{Card, Deck, Rank, Suit};
-    use solitaire_core::{DrawMode, game_state::GameState};
+    use solitaire_core::{DrawStockConfig, game_state::GameState};
 
     /// Build a minimal app with `SelectionPlugin` only — no GamePlugin, no
     /// AssetServer. The `MoveRequestEvent` / `StateChangedEvent` /
@@ -968,7 +968,7 @@ mod tests {
     /// Ace first). It cannot go to an empty tableau (only Kings).
     /// Empty tableaus T3..T6 only accept Kings, so they are filtered out.
     fn deterministic_state() -> GameState {
-        let mut g = GameState::new(0, DrawMode::DrawOne);
+        let mut g = GameState::new(0, DrawStockConfig::DrawOne);
         // Clear stock, waste, all tableaus.
         g.set_test_stock_cards(Vec::new());
         g.set_test_waste_cards(Vec::new());