The .voiceChat AVAudioSession mode defaults to the earpiece, so call audio came
out of the earpiece and only settled after mute/unmute toggling. Switch to
.videoChat + .defaultToSpeaker + allow Bluetooth so audio goes to the loudspeaker
by default while wired/BT headsets still win. Add preferSpeaker() (override to
speaker when on the built-in receiver) in didActivate AND after mic toggles (the
route can flip back to earpiece on unmute). Report the chosen route in telemetry.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>