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

tests/api/health-route.test.ts

@@ -0,0 +1,11 @@
+import { describe, expect, it } from "vitest";
+
+import { GET } from "~/app/api/health/route";
+
+describe("GET /api/health", () => {
+  it("returns 200 and status ok", async () => {
+    const res = await GET();
+    expect(res.status).toBe(200);
+    await expect(res.json()).resolves.toEqual({ status: "ok" });
+  });
+});