feat: Sprint 1 — Playwright e2e + sandbox orchestration (TDD)

- e2e: Playwright chat-flow (sign up -> chat) with api/web webServer harness
- api: sandbox services subset/media-proxy/manifest/gc + DockerClient contract
- api: SandboxManager orchestrator (fake-Docker tested); /health route
- 53 unit tests green; Playwright e2e green

e2e/playwright.config.ts

@@ -0,0 +1,22 @@
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './tests',
+  fullyParallel: true,
+  retries: 0,
+  use: {
+    baseURL: 'http://localhost:5173',
+  },
+  webServer: [
+    {
+      command: 'pnpm --filter @wursor/api start',
+      url: 'http://localhost:3000/health',
+      reuseExistingServer: !process.env.CI,
+    },
+    {
+      command: 'pnpm --filter @wursor/web dev',
+      url: 'http://localhost:5173',
+      reuseExistingServer: !process.env.CI,
+    },
+  ],
+});