0373 — QueueTimeout is renamed QueueMargin; WorkTimeout and AckMargin keep their names

Context. WorkTimeout, QueueTimeout, and AckMargin all sum into leaseDuration, and all three carried “consider a better name” TODOs. Checking actual enforcement, not just the formula, split them into two real categories.

Decision. WorkTimeout and AckMargin are each independently enforced elsewhere — WorkTimeout bounds consumerFunc’s own ctx plus the hard-abandon fallback; AckMargin bounds the Commit/PartialCommit call itself — so their names already match their roles and stay. QueueTimeout was the odd one out: never independently enforced anywhere, pure additive lease padding, structurally identical to AckMargin’s role — renamed QueueMargin to match.

Consequences. The naming TODOs on all three are removed. QueueMargin’s existence (not just its name) hung on the queue/pool-limiter decision; the later buffered-claim-plus-dispatch design kept it with real meaning — time buffered before a processor starts eats the lease, and the bounded buffer is what bounds it.