perf: 小优化组 + 恢复浏览器页签

1. MCP 空闲睡眠 50ms -> 10ms：#187 后单轮 drain 约 0.3ms，
   100 次/s 空闲迭代约 3% 单核，请求与远控输入拾取延迟
   从平均 25ms 降到 5ms。
2. stream 轮询 50ms -> 20ms。
3. stream payload 加 url/title；面板 stream 处理合并 url/
   title，5 秒 state 轮询只在未观看时跑（观看时 stream 已
   全量覆盖，轮询纯冗余；不观看时保留轮询，避免会话开始
   后页眉 stale）。
4. 恢复浏览器页签：#176（ccb5a86）改写 TaskDetailPanel
   页签时顺带删了 BrowserPanel 的挂载，导致线上控制台
   自 #176 起就没有浏览器页签（面板文件一直在，只是不
   被 import，构建产物因此不变）。本次把 import、页签
   与 Card 原样挂回；构建产物含“开始观看”标记可证。
console.html 由 npm run build:console 重打（342484 字节）。
console-redesign/ 为构建脚本审阅产物，不进仓库。

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

@@ -5,6 +5,7 @@ import { shortId, fmt } from "../api/client";
 import { STATUS_EXPLAIN } from "../api/types";
 import { firstChar, durationOf, tokenOf, fmtCostUsd } from "../api/taskMeta";
 import DetailActions from "./detail/DetailActions";
+import BrowserPanel from "./detail/BrowserPanel";
 import ReviewPanel from "./detail/ReviewPanel";
 import { CoordPanel, AgentsPanel, ApprovalPanel, PeerPanel, ThreadPanel } from "./detail/DetailLists";
 
@@ -17,11 +18,14 @@ import { CoordPanel, AgentsPanel, ApprovalPanel, PeerPanel, ThreadPanel } from "
 //   协作：协调子任务 / 子代理链路 / 给其他任务发消息
 //   评审与审批：评审队列 / 运行时审批队列
 //   线程：线程管理
+//   浏览器：浏览器远控（#176 改写页签时顺带掉了本页签，
+//   本次恢复；面板本身一直在 detail/BrowserPanel.tsx，
+//   只是没被挂进页签）。
 // Data, actions and sub-sections are unchanged; only grouping
 // and visibility changed.
-type DetailTab = "overview" | "collab" | "review" | "threads";
+type DetailTab = "overview" | "collab" | "review" | "threads" | "browser";
 const DETAIL_TABS: Array<[DetailTab, string]> = [
-  ["overview", "概览"], ["collab", "协作"], ["review", "评审与审批"], ["threads", "线程"],
+  ["overview", "概览"], ["collab", "协作"], ["review", "评审与审批"], ["threads", "线程"], ["browser", "浏览器"],
 ];
 export default function TaskDetailPanel() {
   const ctx = useConsole();
@@ -113,6 +117,8 @@ export default function TaskDetailPanel() {
       </>) : tab === "review" ? (<>
       <Card title="评审队列"><ReviewPanel /></Card>
       <Card title="运行时审批队列"><ApprovalPanel /></Card>
+      </>) : tab === "browser" ? (<>
+      <Card title="浏览器远控"><BrowserPanel /></Card>
       </>) : (<>
       <Card title="线程"><ThreadPanel /></Card>
       </>)}

cloud/console-react/src/sections/detail/BrowserPanel.tsx

@@ -52,13 +52,22 @@ export default function BrowserPanel() {
     abortRef.current?.abort();
     if (!t) return;
     void refreshState();
-    const timer = setInterval(() => void refreshState(), 5000);
     return () => {
-      clearInterval(timer);
       abortRef.current?.abort();
     };
   }, [t, refreshState]);
 
+  // While watching, the stream payload already carries holder/url/
+  // title at frame rate (plus a 5s heartbeat), so the 5s state
+  // poll would be pure redundancy -- run it only while not
+  // watching, so the header still goes fresh when a session
+  // starts before the user opens the stream.
+  useEffect(() => {
+    if (!t || watching) return;
+    const timer = setInterval(() => void refreshState(), 5000);
+    return () => clearInterval(timer);
+  }, [t, watching, refreshState]);
+
   const startWatch = useCallback(async () => {
     if (!t) return;
     abortRef.current?.abort();
@@ -94,12 +103,18 @@ export default function BrowserPanel() {
               const payload = JSON.parse(line.slice(6)) as {
                 image?: string;
                 holder?: string;
+                url?: string;
+                title?: string;
               };
               if (payload.image) {
                 setImg("data:image/jpeg;base64," + payload.image);
               }
-              if (payload.holder) {
-                setState((s) => ({ ...(s || {}), holder: payload.holder }));
+              const patch: BrowserState = {};
+              if (payload.holder) patch.holder = payload.holder;
+              if (payload.url) patch.url = payload.url;
+              if (payload.title !== undefined) patch.title = payload.title;
+              if (Object.keys(patch).length > 0) {
+                setState((s) => ({ ...(s || {}), ...patch }));
               }
             } catch {
               // ignore a torn frame line