A group's roster changed silently. An add merges on the steward's commit-inactivity timer, and the members that receive its commit apply it, but neither surfaced any observation: Core::wakeup returned () and the client worker discarded it, and GroupV2Convo mapped only chat messages into a ConvoOutcome, so a commit produced an empty outcome. An app could learn a group grew only by re-selecting the conversation, a manual refresh, or a later message from the new member.
de-mls already reports the change: CommitApplied (adds and removes) and WelcomeReady (adds) both fire, on every member, when a commit merges. Drain them into the observation and emit a new event.
- ConvoOutcome gains members_changed, set by GroupV2Convo when a poll cycle's drained de-mls events include CommitApplied or WelcomeReady. It rides alongside content, the same way a protocol-only frame already yields content: None.
- Convo::wakeup returns a ConvoOutcome instead of (), mirroring handle_frame, so the steward's own timer-driven commit is observable. Kinds with no timers return ConvoOutcome::empty; Core::wakeup and the worker translate it through the same events_from_inbound path inbound payloads use.
- New Event::ConversationMembersChanged { convo_id }: the app re-fetches group_members. Fires on every member a commit reaches, so the inviter sees its own add land and existing members see later joins.
