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/hud_plugin.rs

@@ -10,7 +10,7 @@ use bevy::prelude::*;
 use bevy::window::WindowResized;
 use solitaire_core::{Foundation, KlondikePile, Tableau};
 use solitaire_core::card::Suit;
-use solitaire_core::game_state::{DrawMode, GameMode};
+use solitaire_core::{DrawMode, game_state::GameMode};
 
 use crate::auto_complete_plugin::AutoCompleteState;
 #[cfg(not(target_arch = "wasm32"))]
@@ -2726,7 +2726,7 @@ mod tests {
     use crate::game_plugin::GamePlugin;
     use crate::table_plugin::TablePlugin;
     use chrono::Local;
-    use solitaire_core::game_state::{DrawMode, GameState};
+    use solitaire_core::{DrawMode, game_state::GameState};
 
     fn headless_app() -> App {
         let mut app = App::new();