chore(tui): remove unwraps from tui (#9034)
### Description
As https://github.com/vercel/turborepo/issues/9016 displayed, panicking
in the render thread leads to a very poor user experience. We should do
our best effort to avoid this by using errors so we can make sure the
`cleanup` code gets run.
This PR removes (almost) all `unwrap`s/`expect`s in favor of returning
an `Err` which will cause us to exit `run_app_inner`.
### Testing Instructions
Existing unit tests. 👀
