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/components/game/index.ts

@@ -2,11 +2,9 @@
 // Re-exports all game tab components for cleaner imports
 
 // Tab components
-export { CraftingTab } from './tabs/CraftingTab';
-export { SpireTab } from './tabs/SpireTab';
-export { SpellsTab } from './tabs/SpellsTab';
-export { SkillsTab } from './SkillsTab';
-export { StatsTab } from './tabs/StatsTab';
+export { CraftingTab } from './crafting';
+export { SpellsTab } from './SpellsTab';
+export { StatsTab } from './StatsTab';
 
 // UI components
 export { ActionButtons } from './ActionButtons';