The daily recovery reset every dead link to a fresh three-attempt budget,
so a link that can never succeed (an archive too big to import inside the
fetch's hard limit, a file made private) was downloaded up to three times a
day, every day.
Recovery now gives a dead link one more attempt once it has been dead for
2**recoveries days (1, 2, 4, 8, 16), and stops after five. A recovered link
that fails again goes straight back to dead. Retention prunes only links
recovery has given up on, 30 days after their last attempt. A manual refetch
of a post restores the full budgets.
Migration 0118 adds external_link.recoveries.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
