r3pr3ss10n/HandsBusy ? reverse-engineered prompt

Build me a small macOS utility called HandsBusy that runs in the background and stops Bluetooth headphones from stealing my microphone when they connect.

Right now macOS keeps switching the default input to the headphones and that turns on the bad sounding hands free mode. I want the app to watch for microphone changes, and if macOS automatically picks a Bluetooth device, it should switch back right away to my preferred built in or wired microphone. It should only undo the automatic change, not fight me if I manually choose the Bluetooth mic on purpose.

Please make it lightweight, easy to install, and run as a launch agent in the background after login. I’d also like simple install and uninstall scripts so I can set it up and remove it cleanly. If you need to check current macOS or CoreAudio details, look up the latest docs online.