WorkerSnapshot tracked a single failure flag, so a failed /history request
made every later query in the same cycle return None, even for runs the
already-fetched /queue showed as running. A held run that was still
running then accumulated missed probes and had its collect-only delegate
queued before delivery, parking a participating master on it.
Queue and history failures are now tracked separately: queue evidence is
always consulted first, a history failure only affects runs that need
history, and neither endpoint is retried within the snapshot's cycle.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
