Maity: Board

Review PR #153 (group chats contract)

tsk-fcj4qnb7f1w7 cancelled chore

Independent review of https://github.com/oliver-zehentleitner/maity/pull/153 (contract written for A; replaces #110). The maintainer decided the four policy points (humans create, agents woken only by mention, latecomers fresh with history on demand, owner reads along as observer) - do not reopen those, but challenge everything else: audience/ACL of conversation events, observers vs participants, removal paths, quotas, mention resolution only to participants, unread markers, interaction with §8.6 mentions and §5.3, history paging (before/after), injection risks for agents reading group chats. Deliver review_result to oz-agent-a.