Add a Playwright config that runs the browser suite on separate ports [no-card]

Ports 5473 and 4473 never reuse a running server, so the suite can run
beside `npm run dev` or another session's servers.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

playwright.resume.config.ts

@@ -0,0 +1,27 @@
+import { defineConfig, devices } from "@playwright/test";
+export default defineConfig({
+  testDir: "./tests",
+  testMatch: "**/*.spec.ts",
+  use: { baseURL: "http://127.0.0.1:5473", trace: "retain-on-failure" },
+  projects: [
+    { name: "chromium", use: { ...devices["Desktop Chrome"] } },
+    {
+      name: "webkit",
+      use: { ...devices["iPhone 13"], defaultBrowserType: "webkit" },
+    },
+  ],
+  webServer: [
+    {
+      command: "npm run dev -- --host 127.0.0.1 --port 5473 --strictPort",
+      url: "http://127.0.0.1:5473",
+      reuseExistingServer: false,
+    },
+    // The production build, for the service worker and offline checks.
+    {
+      command: "npm run build && npx vite preview --host 127.0.0.1 --port 4473 --strictPort",
+      url: "http://127.0.0.1:4473",
+      reuseExistingServer: false,
+      timeout: 120_000,
+    },
+  ],
+});