Gitea grant executor (steps 0-8, settle, restart, revoke and fire, sweep,
status), the grants.* verbs and mosaic grants, the 3j-3k migration with
gitea_users and gitea_grants, and the section 9 tests with a fake Gitea and
a scratch gitea/gitea:1.27.1 X-G3 test. Build notes in
agents/megavolt/work/queue-236/BUILD.md.
