After validation, the update skill now diffs CHANGELOG.md against the
backup tag to detect [BREAKING] entries. If found, it shows each
breaking change and offers to run the referenced migration skill.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Merge-first workflow that previews upstream changes, lets user choose
full merge / cherry-pick / rebase / abort, resolves only conflicted
files, and validates with build + test.