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/pending_hint.rs

@@ -180,7 +180,7 @@ mod tests {
     use crate::input_plugin::HintSolverConfig;
     use solitaire_core::{Foundation, KlondikePile, Tableau};
     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 Bevy app exercising only the polling system
     /// and the resources/messages it touches.
@@ -209,7 +209,7 @@ mod tests {
     /// foundations hold A..Q for each suit, four Kings sit on
     /// tableau columns 0..3, stock and waste empty.
     fn near_finished_state() -> GameState {
-        let mut game = GameState::new(1, DrawMode::DrawOne);
+        let mut game = GameState::new(1, DrawStockConfig::DrawOne);
         game.set_test_stock_cards(Vec::new());
         game.set_test_waste_cards(Vec::new());
         for foundation in [