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/achievement_plugin.rs

@@ -819,7 +819,7 @@ mod tests {
         app.world_mut()
             .resource_mut::<GameStateResource>()
             .0
-            .draw_mode = solitaire_core::game_state::DrawMode::DrawThree;
+            .draw_mode = solitaire_core::DrawMode::DrawThree;
 
         app.world_mut().write_message(GameWonEvent {
             score: 500,
@@ -868,7 +868,7 @@ mod tests {
         app.world_mut()
             .resource_mut::<GameStateResource>()
             .0
-            .draw_mode = solitaire_core::game_state::DrawMode::DrawThree;
+            .draw_mode = solitaire_core::DrawMode::DrawThree;
 
         app.world_mut().write_message(GameWonEvent {
             score: 500,
@@ -1393,7 +1393,7 @@ mod tests {
 
     use crate::replay_playback::ReplayPlaybackState;
     use chrono::NaiveDate;
-    use solitaire_core::game_state::{DrawMode, GameMode};
+    use solitaire_core::{DrawMode, game_state::GameMode};
     use solitaire_data::{Replay, ReplayMove};
 
     /// Headless app variant that injects a default `ReplayPlaybackState`