rocksolid-0528 — preview smoke test (retry)

This is the template default — a 'use cache' demo backed by per-app Valkey. Refresh repeatedly: if the cache handler works, renderedAt and randomTrace stay identical until the cache expires or a Server Action calls revalidateTag('homepage', 'max').

{
  "renderedAt": "2026-05-30T01:03:47.666Z",
  "randomTrace": "dc5a848d-a996-4a2b-a4e1-b6b4f6707674"
}