Group channel fan-out used event.content only, dropping mediaUrl that
DM handling already merges into message text. Photos with empty captions
in SendBlue groups reached member bots with blank prompts and blocks.
Also skip fan-out when the merged text is empty, matching DM tapback
behavior.
Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: cynarAI <cynarAI@users.noreply.github.com>
Group intros were stamped as posted before the outbox drain ran. When
delivery enqueue failed or the intro row exhausted retries, the channel
stayed marked and no retry path existed — unlinked participants never saw
the onboarding message.
Stamp introPostedAt in the drain path after a successful provider send,
matching the messagingMirroredAt pattern from #42.
Co-authored-by: cynarAI <cynarAI@users.noreply.github.com>
Group inbound webhooks often report only the sender in participants,
not the full roster. Sweeping on any non-empty list incorrectly marked
approved members as left, silently dropping them from channel fan-out.
Gate the sweep on participantsAuthoritative so adapters opt in only when
the provider supplies a complete roster.
Co-authored-by: cynarAI <cynarAI@users.noreply.github.com>
