cleanup: delete computed-stats.ts shim and store/index.ts

- Delete src/lib/game/computed-stats.ts (root-level re-export shim)
- Delete src/lib/game/store/index.ts (nothing imports from it)
- Update __tests__/computed-stats.test.ts to import from ../utils instead
- Clean up craftingStore.ts imports (remove unused useGameStore, CraftingApply)

Typecheck and lint pass (pre-existing DisciplinesTab.tsx errors unchanged)

src/lib/game/__tests__/computed-stats.test.ts

@@ -11,7 +11,7 @@ import {
   computeClickMana,
   getMeditationBonus,
   getIncursionStrength,
-} from '../computed-stats';
+} from '../utils';
 import { MAX_DAY, INCURSION_START_DAY, HOURS_PER_TICK } from '../constants';
 
 describe('fmt', () => {