Support rebuilding releases from existing tags

[unitmatrix]

Summary

• add a manual Release workflow trigger for rebuilding an existing release tag
• build the tagged source while applying current catalog descriptions and documentation
• recreate the multi-platform image, attestations, signature, and GitHub Release without moving the tag
• use the tagged commit SHA consistently in build and release metadata

Validation

• git diff --check
• release workflow YAML parsing
• metadata validation for the existing age and xh release tags