I did that. Customized Pi to run in Bubblewrap, made an action authorization flow, etc. But that's throwing the baby with the bathwater. This gives you a harmless, less capable agent. To get both safety and usefulness, Ant's solution of a fast classifier works really well.

Using Bubblewrap is pretty good. However, I moved to using Apple Containers with one local file directory mounted; When the container is not running, I do git operations outside the container. This is simple, and although not as convenient as running naked with no isolation, it is light weight and easy.

For me, its the other way around.

Strong sandbox + disabling permission checks gives me maximum capabilities, least annoyance and (relative) peace of mind that any prompt injection, malicious plugin,... won't wreck my shit or leak credentials of any kind