sessions.patch for verboseLevel=full was called before the agent RPC
created the session, so it silently failed on new chats. Tool events
were never emitted and the frontend only showed brief text responses.
Now patches both before (for existing sessions) and after the agent RPC
(for newly created sessions). Also adds SSE keepalive to the POST /api/chat
stream to prevent connection drops during long tool executions, and removes
the unused legacy CLI spawn codepath.
36e9cf9517