Add folder game, file browser UI, and automated tests.

Introduces a localStorage-backed messy-desktop challenge with sub-steps,
drag-and-drop and Places/Back navigation, IBM Plex Mono, and a /api/health
endpoint. Adds Vitest coverage for the API and level logic plus Playwright
smoke tests.

Made-with: Cursor

e2e/app.spec.ts

@@ -0,0 +1,25 @@
+import { expect, test } from "@playwright/test";
+
+test.describe("browser", () => {
+  test("home page shows title", async ({ page }) => {
+    await page.goto("/");
+    await expect(
+      page.getByRole("heading", { name: "Folder Game Challenge" }),
+    ).toBeVisible();
+  });
+
+  test("play page loads", async ({ page }) => {
+    await page.goto("/play");
+    await expect(page.getByText("Messy desktop")).toBeVisible({
+      timeout: 15_000,
+    });
+  });
+});
+
+test.describe("API", () => {
+  test("GET /api/health", async ({ request }) => {
+    const res = await request.get("/api/health");
+    expect(res.ok()).toBe(true);
+    await expect(res.json()).resolves.toEqual({ status: "ok" });
+  });
+});