workshop switch and "default" workshop

Maybe this is already a feature and I just missed it, and admittedly this is a very minor thing and just a "nice-to-have".

In a multi-workshop environment (multiple yamls under `.workshop`) it would be nice to have a way to "switch" between them and not have to specify the workshop name for every command.

e.g., something like
```
$ workshop list
WORKSHOP STATUS NOTES
noble Ready default
resolute Ready -

$ workshop run myaction
# runs in 'noble'

$ workshop switch resolute
resolute is now the default workshop

$ workshop list
WORKSHOP STATUS NOTES
noble Ready -
resolute Ready default

$ workshop run myaction
# runs in 'resolute'
```