34aa1991f1
For now, this removes the `#[non_exhaustive]` directive on `EventMsg` so that we are forced to handle all `EventMsg` by default. (We may revisit this if/when we publish `core/` as a `lib` crate.) For now, it is helpful to have this as a forcing function because we have effectively two UIs (`tui` and `exec`) and usually when we add a new variant to `EventMsg`, we want to be sure that we update both.