Make the CLI resolve an omitted environment the same way the server does:
list the catalog once and apply the shared selection helper, instead of
fetching `default`, sniffing the 404, and then listing. Replace the
iterator-count dance in the helper with a slice match, lean on `?` for
error conversion at both call sites, and move the selection error type
into the crate's error module. Document `environment_selection_required`
in the endpoint's error codes and de-duplicate the docs prose.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>