Add vitest setup and puzzleUtils tests

package.json

@@ -5,7 +5,8 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest"
   },
   "dependencies": {
     "fireworks-js": "^2.10.8",
@@ -16,7 +17,10 @@
   },
   "devDependencies": {
     "@vitejs/plugin-vue": "^5.0.4",
+    "@vue/test-utils": "^2.4.6",
+    "jsdom": "^28.0.0",
     "vite": "^5.1.4",
-    "vite-plugin-pwa": "^0.20.5"
+    "vite-plugin-pwa": "^0.20.5",
+    "vitest": "^4.0.18"
   }
 }