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/playwright.config.ts

@@ -0,0 +1,27 @@
+import { defineConfig } from "@playwright/test";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const configDir = dirname(fileURLToPath(new URL(import.meta.url)));
+const frontendRoot = resolve(configDir, ".");
+
+export default defineConfig({
+  testDir: "./tests/e2e",
+  fullyParallel: true,
+  timeout: 30_000,
+  expect: {
+    timeout: 5_000,
+  },
+  use: {
+    baseURL: "http://127.0.0.1:41700",
+    trace: "on-first-retry",
+  },
+  webServer: {
+    command:
+      "pnpm exec vite --config vite.config.ts --host 127.0.0.1 --port 41700 --strictPort",
+    url: "http://127.0.0.1:41700/@vite/client",
+    reuseExistingServer: false,
+    timeout: 120_000,
+    cwd: frontendRoot,
+  },
+});