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/sync_plugin.rs

@@ -604,7 +604,7 @@ mod tests {
     /// would silently drop the link.
     #[test]
     fn upload_result_writes_share_url_into_replay_and_persists() {
-        use solitaire_core::game_state::{DrawMode, GameMode};
+        use solitaire_core::{DrawMode, game_state::GameMode};
         use solitaire_data::{
             Replay, ReplayHistory, load_replay_history_from, save_replay_history_to,
         };