TIL that you can “move” Expo router stacks up into the root easily by re-arranging the file structure.
In some ways this is obvious, but it wasn’t immediately obvious to us as we worked on the problem. We started by manually hiding our tab bar on some screens, but today realized we could take that entire <Stack> and put it at app/(section)/_layout.tsx and it would render entirely over the tabs, which was exactly the behavior we wanted!