read_live_update() read a dead marker, then rechecked it under the marker
mutex in _reclaim_dead(). When a marker-only claimant (the launch hand-off,
no checkout lease) published in between, the recheck correctly kept the
replacement and returned "live" -- but the reader only handled "held" and
fell through to None. update_in_progress() then answered False for a live
update, and the skew watchdog counted that poll toward retirement; the
checkout-lock OR cannot correct it because a marker-only claim holds no
checkout lease.
A "live" recheck verdict now re-judges the marker once and returns its holder.
Review F2 (PR #132365 thread 2).
45a5d646c4