update-pr

Write or update the current branch's GitHub PR title and description via the gh CLI, grounded in the branch diff and commits, preserving existing ticket references. Use for a full rewrite before or after opening a PR, an incremental sync after new commits, or a title-only fix — "update my PR", "refresh the PR description", "sync PR with my changes", "fix the PR title", "write the PR description", "tidy up this PR". This skill is the authority on PR title and body format.