Story 26: Establish TDD workflow and quality gates

Add workflow engine with acceptance gates, test recording, and review
queue. Frontend displays gate status (blocked/ready), test summaries,
failing badges, and warnings. Proceed action is disabled when gates
are not met. Includes 13 unit tests (Vitest) and 9 E2E tests
(Playwright) covering all five acceptance criteria.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/package.json

@@ -8,7 +8,9 @@
     "build": "tsc && vite build",
     "preview": "vite preview",
     "server": "cargo run --manifest-path server/Cargo.toml",
-    "test": "jest"
+    "test": "vitest run",
+    "test:unit": "vitest run",
+    "test:e2e": "playwright test"
   },
   "dependencies": {
     "@types/react-syntax-highlighter": "^15.5.13",
@@ -18,15 +20,20 @@
     "react-syntax-highlighter": "^16.1.0"
   },
   "devDependencies": {
+    "@biomejs/biome": "^2.4.2",
+    "@playwright/test": "^1.47.2",
     "@testing-library/jest-dom": "^6.0.0",
     "@testing-library/react": "^14.0.0",
     "@testing-library/user-event": "^14.4.3",
     "@types/react": "^19.1.8",
     "@types/react-dom": "^19.1.6",
+    "@types/node": "^25.0.0",
     "@vitejs/plugin-react": "^4.6.0",
     "jest": "^29.0.0",
+    "jsdom": "^28.1.0",
     "ts-jest": "^29.0.0",
     "typescript": "~5.8.3",
-    "vite": "^7.0.4"
+    "vite": "^5.4.21",
+    "vitest": "^2.1.4"
   }
 }