Agent Skills: code-review

Multi-agent code review with parallel specialized reviewers, architecture validation, and challenge validation. Use `rq` to request a review of diffs (defaults to main branch), `rs` to respond to PR feedback. Triggers on "review this", "review my code", "code review", "check for bugs", "audit this", when examining PRs, pull requests, branches, or diffs. Supports line-by-line PR comments via gfreview with severity prefixes (Blocker/Issue/Suggestion/Nit). Always asks user before applying fixes or posting responses.