console: 对话只保留一处实时单列（ChatGPT 式）

根因：ConversationSection 同时渲染 TracePanel（prompt +
全部链路条目）和 ContinuePanel（GET /chat-history，
服务端已把 prompt + 继续 + 后续 + 全部链路种类按时间
合并、并去掉了后续消息回声），简单任务的两份名单
显示同一组用户 + 助手卡片，看起来就是对话重复。
改法：删 TracePanel 名单，只留 ContinuePanel 这一列；
TracePanel 唯一不重复的控件（链路类型筛选、下载完整
链路）移到这一列顶部，筛选只过滤链路消息、用户消息
恒保留；实时性不丢：基础是 10 秒轮询的 chat-history，
SSE 新链路条目按 id 去重合并进来，轮询拿到后不再
重复；无 chat-history 的旧服务端回退路径也改成渲染
全部链路种类（不再只渲染 message），并跳过 fu- 回声。

cloud/console-react/src/sections/ConversationSection.tsx

@@ -1,10 +1,12 @@
 import { useConsole } from "../context";
-import TracePanel from "./detail/TracePanel";
 import ContinuePanel from "./detail/ContinuePanel";
 
-// Dashboard conversation section: trace timeline above, continue input
-// below. Dispatch lives in its own section above on the same page, so
-// it is NOT duplicated here when no task is selected — only the hint.
+// Dashboard conversation section: ONE ChatGPT-style conversation column
+// (ContinuePanel). It used to render TracePanel above it, which showed
+// the same user + assistant pair a second time, because chat-history
+// already merges every trace kind into the conversation. Dispatch
+// lives in its own section above on the same page, so it is NOT
+// duplicated here when no task is selected — only the hint.
 export default function ConversationSection() {
   const ctx = useConsole();
   if (!ctx.currentTask) {
@@ -16,8 +18,6 @@ export default function ConversationSection() {
   }
   return (
     <div className="conversation">
-      <TracePanel />
-      <div className="conv-divider" />
       <ContinuePanel />
     </div>
   );