When deliverDelegatedReplies could not resolve the Slack/Teams origin thread,
it still set teamChatMirroredAt and permanently dropped the delegated reply.
Leave the mirror timestamp unset when sourceMessageId exists so reconciliation
retries once the wake chain can be resolved again.
Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: cynarAI <cynarAI@users.noreply.github.com>
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