Should I tell my postdoc advisor I'm intending to leave?
There's nothing standard here. Give as much notice as you can, to be nice, and as much notice as you are legally required to if that's applicable in your jurisdiction. Don't burn a bridge if you don't have to. Even though you are leaving academia, you current boss may have connections to industry that they might be willing to use to help you find a non-academic job, so it might be worth talking to them now rather than when you find something.