grantMicrophoneStatus

Microphone follows the exact same shape as camera — verified against real hardware only for camera so far (ROADMAP.md v2.6.0); this reuses the proven avStatus/avRequestBlocking path rather than a parallel implementation, so what was actually verified end-to-end (the ABI, the completion-handler bridging, the blocking/re-read pattern) is exactly what microphone runs through too — not a second, separately-risked code path.