A repository's forks page lists the forks with the most work to offer first: commits ahead, then fewest behind #5960

The best of a fork tree should rise. /:owner/:name/forks (src/web/pages/repo.ts forksPage) draws forkDrift for each fork.

Done when:

• [ ] Forks are ordered by commits ahead, most first. Ties go to fewest commits behind, then the newest push. Forks with nothing ahead come last, under N forks with nothing new.
• [ ] Each row says N ahead · M behind, and a fork that is ahead links to the compare view, so the work can be offered upstream.
• [ ] Tests: four seeded forks come back in the right order, with the right words. Do not touch src/http/mcp.ts, src/contract/openapi.ts or docs/DESIGN.md.