Extend the WS hello handshake with optional peerType, channel, and model
fields so peers can advertise what kind of client they are. The broker
stores these in-memory on PeerConn and returns them (along with cwd) in
the peers_list response. CLI peers command and MCP list_peers tool now
display the new metadata.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>