Add folder game, file browser UI, and automated tests.

Introduces a localStorage-backed messy-desktop challenge with sub-steps,
drag-and-drop and Places/Back navigation, IBM Plex Mono, and a /api/health
endpoint. Adds Vitest coverage for the API and level logic plus Playwright
smoke tests.

Made-with: Cursor

package.json

@@ -18,6 +18,10 @@
     "lint:fix": "next lint --fix",
     "preview": "next build && next start",
     "start": "next start",
+    "test": "vitest run",
+    "test:e2e": "playwright test",
+    "test:e2e:ui": "playwright test --ui",
+    "test:watch": "vitest",
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {