Summary

Fix the release-notes workflow so changelog update commits created from release events can be pushed back to the release target branch.

Root Cause

The release event checkout lands on the release commit/tag context, so the follow-up git push ran from detached HEAD and failed with:

fatal: You are not currently on a branch.

Changes

• Checkout the release target ref for release-triggered runs, while preserving the current ref for manual dispatch runs.
• Record a target_ref output alongside the resolved release tag.
• Push the changelog commit explicitly with git push origin HEAD:<target_ref>.

Impact

Future release-notes runs should still update the release body and asset, and the changelog commit should no longer fail solely because the runner is detached from a branch.

Validation

• ruby -e 'require "yaml"; YAML.load_file(ARGV.fetch(0)); puts "ok"' .github/workflows/release-notes.yml
• Commit hooks: check yaml, whitespace, EOF, conflict, large-file, and private-key checks passed.
• Re-ran the failed PyPI publish workflow; kida-templates 0.9.0 is now published and PyPI reports it as latest.

Steward Notes

• Consulted steward: .github/AGENTS.md GitHub Workflow Steward.
• Risk: release workflow behavior changes affect changelog publishing on release-created and workflow-dispatch runs.
• Evidence: scoped diff limited to .github/workflows/release-notes.yml; YAML validation and commit hooks passed.
• Unresolved tradeoffs: this PR does not rerun the release-notes workflow because the original release already updated the release body and uploaded RELEASE-NOTES.txt; the changed branch-push path will be exercised by the next release or a manual workflow-dispatch run.