Review a GitHub PR including CI status and review comments

Review PR $1 with the implementation-review skill (find it with skill_select); fetch its diff first via gh pr diff $1. Inspect metadata and files with read-only GitHub commands; do not check out the PR or change branches. Additionally check CI status and failures (gh pr checks $1 / gh run view) and read existing review comments for unresolved threads (gh pr view $1 --comments). Report findings as path:line with severity. Do not edit files.