## Changes
We had a number of copies of test helpers for `io/fs` in the repository.
This change consolidates all of them to use the `libs/fakefs` package.
## Tests
Unit tests pass.
## Changes
This PR adds autocomplete for cat, cp, ls, mkdir and rm.
The new completer can do completion for any `Filer`. The command
completion for the `sync` command can be moved to use this general
completer as a follow-up.
## Tests
- Tested manually against a workspace
- Unit tests