Artifact Hub requires the headlamp/plugin/archive-checksum annotation.
The release workflow's sed replacement (Compute checksum step) expects
this line to already exist in order to substitute the actual SHA256
checksum at release time. Without it, the sed silently does nothing
and AH rejects the package metadata.
Adds an empty placeholder that the release workflow will populate.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Gandalf Greybeard