Show the user messages of the other clients

Show the user messages of the other clients

Each user message event names its source client. The socket clients
submit as terminal, and the terminal client shows a user message from
any other source with the source as a mark, such as "[telegram] text".
With more than one client on one agent, each client then shows the full
conversation, so a reply always comes with its question. The log does
not keep the source.

Issue: a143bd8