Address review on #83878:
- Permanent fatal fences all hold producers and discards pending maps on
teardown instead of re-populating a queue that can never drain.
- Any hold created while connected schedules a tracked redispatch (cancel-
after-pop no longer orphans until a future reconnect).
- Redispatch failures re-hold current + remainder without tight-looping.
Regression coverage for the three residual paths, plus the interaction
with OOF-156's connect-failure classification: the retryable network
path (telegram_connect_error) must NOT clear the hold queue — reconnect
is precisely what drains it; only non-retryable fatals discard.
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