fix: downgrade coverage-v8 and fix vite serving mime types

Author: kochizufan

package.json

@@ -64,7 +64,7 @@
     "@types/node": "^24.10.0",
     "@typescript-eslint/eslint-plugin": "^8.46.3",
     "@typescript-eslint/parser": "^8.46.3",
-    "@vitest/coverage-v8": "^4.0.8",
+    "@vitest/coverage-v8": "^3.0.0",
     "cross-env": "^10.1.0",
     "eslint": "^9.39.1",
     "eslint-config-prettier": "^10.1.8",