On deafen the participant set is snapshotted; on undeafen it is diffed and,
only if it changed and you were deafened for at least 10 s, one auto-dismissing
toast says 'While you were deafened: Alice, Bob joined · Cole left' (names
capped at 3 + N more). Rides the membership stream that already drives the
join/leave sounds — no new subscriptions; PTT holds don't touch deafen so they
can't trigger it. Verified headless: short deafen → nothing; bob leaves during
an 11 s deafen → 'bob left'; long deafen with no change → nothing.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA
