Add a pre-commit check in the rhdh repo's sync-midstream.sh so that before committing the operator bundle we verify all default related images are pullable via skopeo inspect. If any image is not pullable, the script exits with a clear error and does not commit, so we don’t ship a bundle that can break installs.

Scope

• Minimum: Verify the default plugin-catalog-index image (from rhdh-default-config_v1_configmap.yaml – CATALOG_INDEX_IMAGE) is pullable.
• Repeat for the other related images in the CSV. Extend to other related images (hub, operator, postgres) so that ALL related_image refs in the bundle is validated.

Acceptance criteria

• Running sync-midstream.sh with a bundle that references a non-pullable image (e.g. wrong registry or missing image) causes the script to exit without committing.
• Error message clearly states which image failed and references this check