fix: suppress vitest-pool-workers debug noise and hanging process

- Pre-declare Node.js compatibility flags in miniflare config to
  prevent [vpw:debug] messages during test runs
- Use --no-file-parallelism to fix dangling handle causing
  "close timed out" warning on exit

package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "dev": "wrangler dev",
     "deploy": "wrangler deploy",
-    "test": "vitest run",
+    "test": "vitest run --no-file-parallelism",
     "test:watch": "vitest"
   },
   "repository": {