PR self-review notes

Read the diff as a reviewer and answer the few questions the code cannot answer for itself. Zero notes is a good result when the change is already clear. Most PRs need zero to three; larger or unusually subtle changes may need more.

These are quick asides to a teammate, not documentation or a defense of the change.

1. Establish the target and authorship

Default to the PR for the current branch. If the user names a PR number or URL, use that target and its repository for every command.

gh pr view \
  --json number,title,body,author,headRefName,headRefOid,state,url
gh api user --jq .login