macOS 27 beta's AUHAL rejects mpv's channel-layout property with paramErr
(-50), so the coreaudio AO fails to initialize and playback is silent.
Change the macOS ao option from "coreaudio" to "coreaudio,avfoundation"
so mpv self-heals: older macOS keeps using coreaudio unchanged, while the
beta drops to avfoundation (AVSampleBufferAudioRenderer) instead of playing
no sound.