ci: dispatch release workflow after automated tag

[sionsmith]

Summary

• Add workflow_dispatch to the Release workflow so it can be triggered explicitly for a tag
• Make Release publishing only happen for tag refs, preventing accidental manual branch releases
• Update Release Tagger to create/verify the tag, dispatch release.yml explicitly, and fail if a release run is not observed
• Stop relying on tag-push workflow fan-out from inside GitHub Actions

Verification

• YAML parsed with Ruby for release.yml and release-tagger.yml
• git diff --check
• gh run list --workflow release.yml --event workflow_dispatch --commit 784b31c --limit 1 --json createdAt,url