console: 任务列表服务端分页 + 控制台分页面签

任务列表分页（服务端 + 前端）：
- GET /tasks 新增 limit（1..100，非法回 400）、offset、
  order=desc、status/executor/q 服务端过滤；回 total（过滤后
  计数）与 status_counts（全项目统计，不受过滤与分页影响，
  数据卡片不再把当前页当成全项目）；无 limit 时旧行为不变
  （全量、正序，协调子任务与旧调用不受影响）。
- 前端每页 20 条、最新在前，上一页/下一页 + 页码；筛选与
  搜索改服务端过滤（搜索防抖 300ms），切筛选/切项目/派发
  后回第 1 页，10 秒刷新与刷新按钮停在当前页；新测试
  test_task_list_pagination.py 5 项。

分页面签：
- 顶栏锚点导航改成 5 个页签：工作台（派发 + 任务列表 +
  对话 + 详情）、项目（项目 + 成员）、环境与 Workers、
  技能与自动化（技能 + 自动化 + 分诊）、管理与 Key；
  数据卡片仍在页签上方常驻。选中任务存在 App 层 store
  里，切页不丢，回来仍是同一任务、10 秒刷新续同步；
  页签同步到 location.hash（#tab-workbench 等），刷新与
  分享链接落在同一页签；窄屏工作台仍保持派发在前的顺序。
- 工作台页签仍是左（任务）右（派发/对话/详情）两栏，
  沿用等高内部滚动规则；其它页签单列堆叠。

cloud/server.py

@@ -4495,6 +4495,17 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
         self._send_json(201, task)
 
     def _list_tasks(self, user_id, query):
+        # GET /tasks: server-side pagination + filtering.
+        # - No limit param: old behaviour, all rows in created_at
+        #   order (coord children and existing callers rely on it).
+        # - limit param: limit 1..100, offset >= 0 (invalid -> 400),
+        #   order=desc (newest first, the list's display order),
+        #   status/executor exact match, q case-insensitive
+        #   substring over id + prompt (same rule the frontend
+        #   used to apply client-side). total is the filtered
+        #   count before slicing, status_counts is over all
+        #   project rows (so the data card's breakdown is not
+        #   skewed by the current filter or page).
         project_ids = query.get("project_id")
         project_id = project_ids[0] if project_ids else None
         if not project_id:
@@ -4508,6 +4519,22 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
         parent_ids = query.get("parent_task_id")
         if parent_ids:
             parent_task_id = parent_ids[0]
+        limit = None
+        offset = 0
+        if query.get("limit"):
+            try:
+                limit = int(query["limit"][0])
+                offset = int(query["offset"][0]) if query.get("offset") else 0
+            except (TypeError, ValueError):
+                self._send_json(400, {"error": "limit/offset must be integers"})
+                return
+            if limit < 1 or limit > 100 or offset < 0:
+                self._send_json(400, {"error": "limit must be 1..100, offset >= 0"})
+                return
+        order_desc = bool(query.get("order") and query["order"][0] == "desc")
+        status_f = query["status"][0] if query.get("status") else None
+        executor_f = query["executor"][0] if query.get("executor") else None
+        q_f = query["q"][0].lower() if query.get("q") else None
         conn = self._db()
         try:
             if parent_task_id:
@@ -4523,13 +4550,38 @@ class CloudControlPlaneHandler(BaseHTTPRequestHandler):
                     " ORDER BY created_at, id",
                     (project_id,),
                 ).fetchall()
-            amap = _attachments_map(conn, [r["id"] for r in rows])
-            tmap = _task_tokens_map(conn, [r["id"] for r in rows])
+            status_counts = {}
+            for r in rows:
+                s = r["status"]
+                status_counts[s] = status_counts.get(s, 0) + 1
+            if parent_task_id:
+                filtered = rows
+            else:
+                filtered = []
+                for r in rows:
+                    d = _task_to_dict(r, [], 0)
+                    if status_f and d["status"] != status_f:
+                        continue
+                    if executor_f and (d["executor"] or "") != executor_f:
+                        continue
+                    if q_f and q_f not in ((d["id"] or "") + " " + (d["prompt"] or "")).lower():
+                        continue
+                    filtered.append(r)
+            total = len(filtered)
+            if order_desc:
+                filtered = list(reversed(filtered))
+            page_rows = filtered[offset:offset + limit] if limit is not None else filtered
+            amap = _attachments_map(conn, [r["id"] for r in page_rows])
+            tmap = _task_tokens_map(conn, [r["id"] for r in page_rows])
         finally:
             conn.close()
-        self._send_json(200, {"tasks": [
+        out = {"tasks": [
             _task_to_dict(r, amap[r["id"]], tmap.get(r["id"], 0))
-            for r in rows]})
+            for r in page_rows], "total": total, "status_counts": status_counts}
+        if limit is not None:
+            out["limit"] = limit
+            out["offset"] = offset
+        self._send_json(200, out)
 
     def _fetch_task(self, task_id):
         conn = self._db()