Maity: Board

Review PR #158 (availability, cover, rate-limit wake)

tsk-paq7sfwshafw cancelled chore

Independent review of https://github.com/oliver-zehentleitner/maity/pull/158 (contract for A). Focus: cover can never escalate rights or make a member review its own work, claim transfer races, request on_behalf_of semantics, coordinator_unavailable effects, runner rate_limited state vs crash cap, event audiences, §2.3 humans_only invariant. Deliver review_result to oz-agent-a.