Fix critical bugs, add test framework, improve code quality

- Fix syntax errors with missing brackets in store.ts and crafting-slice.ts
- Fix state mutation issues with lootInventory deep cloning
- Remove race condition from mid-tick set() call
- Fix COMBO_MASTER using wrong counter (totalTicks vs totalSpellsCast)
- Add null safety to hasSpecial() function
- Clamp mana to 0 in deductSpellCost() to prevent negative values
- Set up Vitest testing framework with 36 passing tests

package.json

@@ -7,6 +7,8 @@
     "build": "next build && cp -r .next/static .next/standalone/.next/ && cp -r public .next/standalone/",
     "start": "NODE_ENV=production bun .next/standalone/server.js 2>&1 | tee server.log",
     "lint": "eslint .",
+    "test": "vitest",
+    "test:coverage": "vitest --coverage",
     "db:push": "prisma db push",
     "db:generate": "prisma generate",
     "db:migrate": "prisma migrate dev",
@@ -82,13 +84,17 @@
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.2",
     "@types/react": "^19",
     "@types/react-dom": "^19",
     "bun-types": "^1.3.4",
     "eslint": "^9",
     "eslint-config-next": "^16.1.1",
+    "jsdom": "^29.0.1",
     "tailwindcss": "^4",
     "tw-animate-css": "^1.3.5",
-    "typescript": "^5"
+    "typescript": "^5",
+    "vitest": "^4.1.2"
   }
 }