fix(webui): broadcast runtime model updates

Co-authored-by: Cursor <cursoragent@cursor.com>

webui/src/hooks/useNanobotStream.ts

@@ -44,7 +44,6 @@ export function useNanobotStream(
   initialMessages: UIMessage[] = [],
   hasPendingToolCalls = false,
   onTurnEnd?: () => void,
-  onModelNameChange?: (modelName: string | null) => void,
 ): {
   messages: UIMessage[];
   isStreaming: boolean;
@@ -182,9 +181,6 @@ export function useNanobotStream(
       }
 
       if (ev.event === "message") {
-        if (ev.model_name !== undefined) {
-          onModelNameChange?.(ev.model_name || null);
-        }
         if (
           suppressStreamUntilTurnEndRef.current &&
           (ev.kind === "tool_hint" || ev.kind === "progress")