Release the macOS mic indicator when idle

[karansinghgit]

Summary

• stop prewarmed audio capture sessions automatically after a short idle window
• cancel any pending idle shutdown once a real recording starts and force the session fully off when recording ends
• stop the capture session when the mini recorder disappears so the menu-bar mic indicator does not linger

Validation

• xcodebuild build -scheme speaktype -destination 'platform=macOS'

Notes

• this still needs a manual hold-mode repro check on macOS to confirm the orange mic indicator disappears after transcription completes