fix: align task backend filters on desktop

frontend/src/components/pages/ComponentsTaskBackendsPage.tsx

@@ -129,8 +129,17 @@ export function ComponentsTaskBackendsPage() {
     <ListPageLayout title="任务后端" description="为提示词助手配置独立的推理与执行环境。Speaker 负责对话，任务后端负责处理委派目标。"
       action={<Button className="gap-2" disabled={loading || Boolean(error)} onClick={() => openEditor()}><Plus size={16} />添加任务后端</Button>}>
       <ListPageSection>
-        <ListToolbar filters={<FilterPills options={filters} value={filter} onChange={setFilter} />}
+        <ListToolbar
-          search={<SearchInput value={search} onChange={setSearch} placeholder="搜索任务后端" />} />
+          filters={<FilterPills options={filters} value={filter} onChange={setFilter} />}
+          search={
+            <SearchInput
+              value={search}
+              onChange={setSearch}
+              placeholder="搜索任务后端"
+              className="lg:w-[320px] lg:shrink-0"
+            />
+          }
+        />
         <DataList rows={filtered} rowKey={resource => resource.id} loading={loading} error={error} onRetry={() => void load()}
           onRowClick={resource => { if (busyId !== resource.id) openEditor(resource); }} empty={{ title: "暂无任务后端", description: "创建内置 Reasoner 或外部 OpenCode，再到提示词助手中绑定。" }}
           columns={[