Make the "Test audio" connectivity check pod-wide instead of local to the
publisher. Shared on/off state is derived from the presence of the podman-beat
track across participants (self-syncing on join/leave). Any participant can
stop it: the owner unpublishes directly; non-owners send a new additive
BEAT_STOP data message that the owner honors. Drives the button label, status
line, and status waveform for everyone, and guards against rapid-double-click
double-publish and mid-start unmount leaks.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Kartikeya