Returns up to limit of a user's newest videos (published_at DESC, NULLS LAST)
that have no summary yet. RLS-scoped via withUser — the test proves a second
user's newer video never leaks. Drives the connect-time onboarding burst
(Feature 1); the caller routes each through the shared rate gate.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>