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/server.py

@@ -5318,11 +5318,14 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
     def _browser_stream(self, user_id, task_id):
         """GET /tasks/{id}/browser/stream: SSE from bridge files.
 
-        Polls the frame file every 50ms and emits a data line
+        Polls the frame file every 20ms and emits a data line
         whenever its bytes change (plus a heartbeat with the
-        current holder at least every 5s). Ends the stream when
-        the state file goes stale, so a dead session reads as a
-        disconnect, not a frozen picture.
+        current holder at least every 5s). The payload also
+        carries the session url/title, so the console panel can
+        track the header from the stream alone instead of
+        polling the state endpoint while watching. Ends the
+        stream when the state file goes stale, so a dead
+        session reads as a disconnect, not a frozen picture.
         """
         import time
         from cloud.playwright_remote import (
@@ -5360,11 +5363,13 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                     payload = json.dumps(
                         {"image": frame,
                          "holder": effective_holder(worktree, state),
+                         "url": state.get("url", ""),
+                         "title": state.get("title", ""),
                          "ts": int(now)}, ensure_ascii=False)
                     self.wfile.write(
                         ("data: %s\n\n" % payload).encode("utf-8"))
                     self.wfile.flush()
-                time.sleep(0.05)
+                time.sleep(0.02)
         except (BrokenPipeError, ConnectionResetError, OSError):
             pass