chore(tui): remove unwraps from tui (#9034)

### Description

As #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. 👀