Rewrite a thin or missing pull-request description (title + body) in the repo's own PR voice, learned from its merged-PR history — title convention, section shape, length for the diff size, how issues get closed. Grounded in the actual diff; never invents testing claims or motivation. Shows a before/after and applies with `gh pr edit` only on explicit confirmation. Use when the user asks to write, rewrite, fill in, or clean up a PR description, or to draft one for the current branch before opening a PR.