0164 — Reclaim drains before fresh claim, one expired lease per poll

Context. With leases in place a poll could either pick up new frontier work or recover a crashed worker’s expired lease; the order determines how long an unresolved gap pins the waterline.

Decision. ClaimMessagesWithCursor runs ReclaimWithCursor first — take one expired lease (until < now(), LIMIT 1 FOR UPDATE SKIP LOCKED) and re-read its exact (low, high] range under a fresh token — and falls through to FreshClaimMessagesWithCursor only when nothing is reclaimable.

Consequences. A crashed range is older work; draining it first keeps committed moving and bounds how far claimed runs ahead of an unresolved gap. One reclaim per poll is enough — a backlog of expired leases bleeds down across successive polls. The original delete-then-insert reclaim shape was later replaced by a single atomic UPDATE (see 0190); the reclaim-before-claim ordering stands.