refactor(core): move solver to solitaire_data, DrawMode to klondike_adapter, remove pile/solver/schema_version

- Delete solitaire_core::solver — moved wholesale to solitaire_data::solver (re-exported at crate root)
- Delete solitaire_core::pile — no external users
- Move DrawMode from game_state to klondike_adapter; re-export as solitaire_core::DrawMode
- Remove schema_version field from GameState (redundant — deserializer stamps it from the constant)
- Update all callers across solitaire_data, solitaire_engine, solitaire_assetgen, solitaire_wasm

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/stats_plugin.rs

@@ -1327,7 +1327,7 @@ mod tests {
         app.world_mut()
             .resource_mut::<crate::resources::GameStateResource>()
             .0
-            .draw_mode = solitaire_core::game_state::DrawMode::DrawThree;
+            .draw_mode = solitaire_core::DrawMode::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::game_state::DrawMode::DrawOne,
+            solitaire_core::DrawMode::DrawOne,
             solitaire_core::game_state::GameMode::Classic,
             time_seconds,
             0,