Publish floating major Action tag @v0 for compare composite action

[cursor]

Summary

docs/github-action.md mentions a floating @v0 pin once a moving major tag exists. Releases are exact (v0.4.0) only.

Acceptance criteria

• Document process: on each v0.x.y release, move v0 tag to the same commit (or automate in publish workflow)
• Create/update v0 tag for current latest 0.x release
• Example snippet in docs/github-action.md shows both @v0.4.0 (preferred) and @v0 (convenience)
• Note that @v0 can still receive breaking 0.x changes

Caution

• Moving tags need force-push permissions — implement carefully in publish.yml or a documented maintainer step