0.0.21

Hang-proof meeting detection: timeout the mic check

The poll loop awaited _inMeeting() with no upper bound. If michelper
wedged (common after sleep/wake or a CoreAudio hiccup), that await never
resolved, the finally never ran, and detection froze permanently — the
log went silent while the mic stayed active and the Split/Stop bar never
appeared.

Race _inMeeting() against a 6s hard timeout in poll() (treat a timeout
as "no signal" and carry on), and force-kill michelper if its execFile
callback never fires so its promise can't hang.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>