getWebAudioChannelCount function
Returns the number of channels the browser mic stream provides. Uses getUserMedia constraints to check.
Implementation
int getWebAudioChannelCount() {
// On web, flutter_sound requests mono but browsers may deliver stereo.
// The AudioContext itself doesn't tell us — the MediaStream does.
// For now, we rely on the sample rate being correct (which it is via
// AudioContext.sampleRate) and handle channel count via the data format.
// Most browsers deliver mono when mono is requested in getUserMedia.
return 1;
}