A visually hidden aria-live=polite region (rendered by CallEmbedProvider so it
outlives the embed) announces joins/leaves — batched over 1.5 s: 'alice
joined', 'alice and bob joined', '3 people joined' — your own mute/unmute,
deafen/undeafen and screenshare start/stop, and 'Call ended'. Nothing visible,
nothing audible for anyone else, no setting. Verified headless by observing
the region: bob joined → You are muted → … → bob left → Call ended.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA
