Track viewers by endpoint id instead of a bare count. The JSON event
stream gains viewer_joined / viewer_left (each carrying the id),
replacing viewer_count; active/max still ride along so the count
display is unchanged.
The host screen now renders one row per connected viewer with a Kick
button. Clicking it sends `kick <id>` to the headless child over a new
stdin command channel, which the host turns into a per-viewer
CancellationToken cancel; the existing teardown path then emits the
leave, so a kick and a self-disconnect look identical downstream.
The stdin channel only runs under --output json (the GUI shell-out) and
on a detached OS thread, so a read parked on stdin can't hold up the
host's Ctrl+C shutdown.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
mollusk
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