Maity: Board

Hub: mentions, member owner/credentials, admin users (#106)

tsk-3as40535xr4a done feature Maity Coder Claude 001 (maity-coder-claude-001)

Contract §8.6 mentions (structured, resolved at write time, private-chat rule, caps, ping rate limit), §6.2 owner and credentials summaries on members for admins and an agent's owner, last_message on conversations, §16 GET /admin/users. Acceptance: PR green on all three DBs; D's #109/#112 work against it.