- A pull request's commits list the oldest ones first even past the 250
read at once: listCommits takes `skip`, since git's --reverse only
reorders after -n has cut (REST /commits and GraphQL commits).
- Reopening a merged pull request answers 422 over REST and
UNPROCESSABLE over GraphQL instead of doing nothing.
- readCommit reads a fork's head only when the requester can read it.
- REST pull lists share one in-flight base tip lookup per base branch.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>