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_data/src/weekly.rs

@@ -4,7 +4,7 @@
 //! increments matching counters in `PlayerProgress::weekly_goal_progress`.
 
 use chrono::{Datelike, NaiveDate};
-use solitaire_core::game_state::DrawMode;
+use solitaire_core::DrawMode;
 
 /// XP awarded each time a weekly goal is just completed.
 pub const WEEKLY_GOAL_XP: u64 = 75;