ci: use workflow ref for ArtifactHub dispatch

[KeiaiLab-PHIL]

Summary

• stop overriding checkout ref in ArtifactHub verify
• tag push still checks out the tag by default
• workflow_dispatch now uses the selected workflow ref, so backfill runs can use latest smoke retry logic while validating the requested tag/version

Validation

• actionlint .github/workflows/artifacthub-verify.yml
• git diff --check