Hi, nsec.app and bunker-urls have nothing to do with browser extensions. Every time you log in to an app, the app generates a temporary nsec/npub which is used to connect to your keys inside nsec.app (and that temporary npub you see in connection requests). Each time a connection is established the new key is generated by an app, and you have to approve it in nsec.app. Limited shared access is impossible atm - you'd need to basically give your friends full access to nsec.app so that they themselves would be able to approve the connection requests without your help. I have limited shared access feature outlined on the roadmap, but it's actually quite hard to implement and you're only a second person to ask for it, so I guess it will take a while before we start working on it.
Can you please tell me more about what your expectation was with browser extensions + nsec.app? Did you mean nsec stored in extension would somehow be "allowed" in nsec.app and then something good could happen? Thanks.