Two daemon-side fixes to the persisted task transcript:
- Wait for the drain goroutine to flush the final message batch before every
terminal return (result, timeout, idle-watchdog, upstream cancel), so a
consumer reading the transcript at completion can't see a truncated tail.
Bounded (10s, then cancel + 12s) so a backend that never closes its message
channel cannot stall the terminal transition.
- Share the message seq counter across a resume-failure retry so the retry's
rows keep ascending seq values instead of restarting at 1 and interleaving
with the failed attempt's rows.
Server-initiated cancellation read timing is tracked separately in #5219.
Closes#5209
MUL-4369
7a405fd1cf