React with emoji for better UX on explicit review ask - #62

Adds a best-effort 👀/👍 reaction lifecycle for explicit @seidroid review requests; the design is sound (gated behind authorization, all GraphQL calls wrapped in try/catch so failures only warn). Findings are non-blocking: a likely missing issues: write scope on the GITHUB_TOKEN fallback path, a stale-👀 case when a run is cancelled, and no signal to the requester when the review fails.