This may not be popular, but is there a place for required human actions or just timed actions to slow down things like this? For instance, maybe a GH action to deploy requires a final human click and to change that to cli has a 3 day cooling period with mandatory security emails sent out. Similarly, you switch to read only for 6 hrs after an email change. There are holes in these ideas but the basic concept is to treat security more like physical security, your goal isn't always to 100% block but instead to slow an attacker for xxx minutes to give the rest of the team time to figure out what is going on.