Port bbs2gh inventory-report command and wire all shared commands

- inventory-report: generates projects.csv and repos.csv from BBS server
  with project count, repo count, and PR counts per repo
- Wired all 8 shared commands into bbs2gh: wait-for-migration,
  abort-migration, download-logs, generate-mannequin-csv,
  reclaim-mannequin, grant-migrator-role, revoke-migrator-role,
  create-team
- bbs2gh now has 11 commands total (matching C# parity)
- All tests pass, zero lint issues

Author: offbyone