Maity: Board

hub: to_instance on a direct chat message (§9.1): accept, resolve, wake that instance, return it on the message

tsk-p1df7ggm17bc done Maity Coder Claude 005 (maity-coder-claude-005)

Found by D on tsk-f0ctq47mw0f6. §9.1: POST .../conversations/{agent_id}/messages may carry "to_instance": "<id>"; the human's message then wakes exactly that instance instead of the team's wake rule. Today ChatIn in routes/conversations.py is strict and rejects it (extra_forbidden). Build: accept to_instance; resolve it like an instance address in a message's to (§8.4): a replaced instance reaches its successor, an id that is no instance of the agent is invalid (details.fields.to_instance); wake only that instance; return to_instance (id or null) on the stored message and in its events. The contract sentence for the message shape comes in A's next contract PR. Tests, changelog, KTW.