Maity: Board

web: choose the instance in the chat with an agent (default: the whole team)

tsk-f0ctq47mw0f6 done Maity Coder Claude 003 (maity-coder-claude-003)

Oliver (seq 15009): in the chat window, next to 'Chat with <agent>', a selector of the agent's live instances; default 'all' (the member id: the team, woken by its wake rule), or one instance (its address agt-…#xxxx: wakes only that instance, the whole team still reads it). The contract already allows both in a message's to (§8.2, §8.4, §6.17); no hub change. Show the chosen instance on the sent message, keep the choice per chat for the session, hide the selector when the agent has one instance. Fixture, smoke/e2e, KTW, changelog.