build(web): upgrade Vitest 3→4 (browser-playwright provider) (#46)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/package.json

@@ -51,8 +51,8 @@
     "@types/react": "^19.1.5",
     "@types/react-dom": "^19.1.3",
     "@vitejs/plugin-react": "^4.5.2",
-    "@vitest/browser": "3.2.6",
-    "@vitest/coverage-v8": "3.2.6",
+    "@vitest/browser-playwright": "^4.1.8",
+    "@vitest/coverage-v8": "4.1.8",
     "eslint": "^10.4.1",
     "eslint-plugin-react-hooks": "^7.1.1",
     "eslint-plugin-react-refresh": "^0.5.2",
@@ -69,7 +69,7 @@
     "typescript": "~5.8.3",
     "typescript-eslint": "^8.60.1",
     "vite": "^6.3.5",
-    "vitest": "^3.2.2"
+    "vitest": "^4.1.8"
   },
   "msw": {
     "workerDirectory": [