I want to be able to check the status of the pipeline at a specific git ref to ensure artifacts at that ref are not stale

One possible way to do this is to manually check it out and then run `calkit status`, but could we add a `--ref` option to `status` to make it quicker?

Start at the `calkit status` command entry point and trace how it determines the Git ref being inspected. Check how CLI options and status tests are organized, then verify completion by confirming that `--ref` reports pipeline and artifact status for the requested ref without requiring a checkout.

Written by the indexing model from the issue text.