When runSubagentAnnounceFlow returns false (deferred), finalizeSubagentCleanup
resets cleanupHandled=false and removes from resumedRuns, allowing
retryDeferredCompletedAnnounces to pick it up again. If the underlying
condition persists (stale registry data, transient state), this creates an
infinite loop delivering 100+ announces over hours.
Fix:
- Add announceRetryCount + lastAnnounceRetryAt to SubagentRunRecord
- finalizeSubagentCleanup: after MAX_ANNOUNCE_RETRY_COUNT (3) failed attempts
or ANNOUNCE_EXPIRY_MS (5 min) since endedAt, mark as completed and stop
- resumeSubagentRun: skip entries that have exhausted retries or expired
- retryDeferredCompletedAnnounces: force-expire stale entries
