feat(frontend): 广场搜索体验优化与切换tab重置筛选

- 智能体广场：切换 我的/广场/私密广场 时清空重置搜索/标签/排序/发布者筛选
- 通用搜索栏(TagSearchBar)：新增「搜索」按钮与回车立即触发(跳过防抖)、
  搜索中转圈提示，新增 hideTags / searchPlaceholder 选项
- 定时任务广场：新增客户端搜索(名称/摘要/创建者，兼容脱敏文本)
- agents 分页 hook 暴露 isFetching 以驱动搜索中状态

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/pages/ScheduledTasksPage.tsx

@@ -149,13 +149,16 @@ export default function ScheduledTasksPage() {
   const initialTaskId = searchParams.get("task");
   const [search, setSearch] = useState("");
   const [tagIds, setTagIds] = useState<string[]>([]);
+  // Plaza (广场) name search is resolved client-side over the fetched published
+  // list, kept separate from the server-side 我的任务 search above.
+  const [plazaSearch, setPlazaSearch] = useState("");
   // Publisher (创建者) filter for the 我的任务 tab — click a task's 创建者 to keep
   // only that creator's tasks. {id} is creator_user_id; {label} the display name.
   const [publisher, setPublisher] = useState<{ id: string; label: string } | null>(
     null,
   );
   // Name + tag filtering is resolved server-side via the /api/scheduled-tasks query.
-  const { data: tasks = [], isLoading } = useScheduledTasks({ search, tagIds });
+  const { data: tasks = [], isLoading, isFetching } = useScheduledTasks({ search, tagIds });
   const { data: deliveryProfile } = useScheduledTaskDeliveryProfile();
   const { agents } = useAgents();
   const actions = useScheduledTaskActions();
@@ -215,6 +218,24 @@ export default function ScheduledTasksPage() {
         : sortedTasks,
     [sortedTasks, publisher],
   );
+  // Plaza search: filter the fetched published list client-side. Match against
+  // both the raw and desensitized forms so typing what's shown on screen (the
+  // desensitized name) and the underlying text both hit.
+  const visiblePublished = useMemo(() => {
+    const q = plazaSearch.trim().toLowerCase();
+    if (!q) return published;
+    return published.filter((item) =>
+      [
+        item.name,
+        desensitize(item.name),
+        item.prompt_summary,
+        desensitize(item.prompt_summary ?? ""),
+        item.schedule_text,
+        displayUsername(item.creator_email),
+      ].some((field) => (field ?? "").toLowerCase().includes(q)),
+    );
+  }, [published, plazaSearch]);
+
   const selectedTask = sortedTasks.find((task) => task.task_id === selectedTaskId) ?? null;
   const selectedTaskCanEditRuns = !!selectedTask && selectedTask.role !== "subscriber";
   const { data: runs = [], isLoading: runsLoading } = useScheduledTaskRuns(selectedTaskId);
@@ -465,6 +486,16 @@ export default function ScheduledTasksPage() {
                   onSearchChange={setSearch}
                   tagIds={tagIds}
                   onTagIdsChange={setTagIds}
+                  searching={isFetching}
+                />
+              )}
+              {activeTab === "plaza" && (
+                <TagSearchBar
+                  targetType="scheduled_task"
+                  hideTags
+                  onSearchChange={setPlazaSearch}
+                  searching={publishedLoading}
+                  searchPlaceholder="搜索广场任务（名称 / 摘要 / 创建者）"
                 />
               )}
               {activeTab === "mine" && publisher && (
@@ -751,14 +782,19 @@ export default function ScheduledTasksPage() {
                 ) : (
                   <div className="flex flex-col gap-3 p-4 pt-0">
                     {publishedLoading && (
-                      <div className="text-muted-foreground text-sm">正在加载广场任务...</div>
-                    )}
-                    {!publishedLoading && published.length === 0 && (
-                      <div className="text-muted-foreground rounded-md border p-4 text-sm">
-                        广场上还没有发布的任务。
+                      <div className="text-muted-foreground flex items-center gap-2 text-sm">
+                        <Loader2 className="size-4 animate-spin" />
+                        正在加载广场任务...
                       </div>
                     )}
-                    {published.map((item) => {
+                    {!publishedLoading && visiblePublished.length === 0 && (
+                      <div className="text-muted-foreground rounded-md border p-4 text-sm">
+                        {plazaSearch.trim()
+                          ? `没有匹配「${plazaSearch.trim()}」的任务。`
+                          : "广场上还没有发布的任务。"}
+                      </div>
+                    )}
+                    {visiblePublished.map((item) => {
                       const subscribed = tasks.some((t) => t.task_id === item.task_id);
                       return (
                         <div key={item.task_id} className="bg-card rounded-md border p-4">