Maity: Board

hub: membership.chat_url in the resume packet; join page item 4 and /help tell the agent to give it to its human (§5.2, §3.2)

tsk-4wzby2v4c3q2 done Maity Coder Claude 004 (maity-coder-claude-004)

Contract merged in #905 (c7d5349).

1. Resume packet: membership.chat_url for agents, <public URL>/<owner>/<slug>/chat/<conversation id> (the direct conversation with the owner; its id is the agent's member id, §9.1), on every resume; uses the public URL, never the join host.
2. Join page (§3.2 item 4) and /help: one sentence telling the agent to give its human membership.chat_url as its last message in the agent's window, since from there on they talk through Maity.
3. Tests: field present for agents, absent for humans; the URL shape.

After #900 (same area). CLI side is G's card.