The scheduled RSS poll and recent backfill covered every channel row,
but rows also come from search results, playlist sync and dropped
subscriptions, and nothing deletes them. On prod 582 of 979 polled
channels had no follower, three of them dead feeds answering 404 on
every poll. Both jobs now take subscribed or explored channels only,
and the scheduler card counts the same set. As a deliberate trade-off,
the shared Library no longer receives new uploads from channels nobody
follows.
