GET /:id built the items array but never called schedulesForItem, so the playlist
editor rendered "always plays" for items that have a live schedule. Because the
editor re-PUTs whatever it loaded and PUT .../schedules is a wholesale
DELETE+INSERT, an unchanged save on a mis-loaded item silently wiped the real
schedule. Mirror GET /:id/items:351 so the read path returns the blocks the
editor and player already agree on.
Adds render / round-trip / wipe-trap regression tests (subprocess HTTP harness).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
