feat: 对话列表显示总数，SOUL 编辑区高度自适应收敛

- 新增 POST /threads/count：与 /threads/search 同一套过滤（标题搜索、
  系统会话排除），仅返回 {total}；ThreadMetaStore 增加 count 方法
  （SQL 走 COUNT(*)，JSON 过滤分批扫描计数）
- 对话页面搜索框下常驻显示「共 N 条对话」，分页条显示 当前页/总页数
  （useThreadsCount，仅随筛选条件变化，翻页不重复请求）
- 智能体右侧 SOUL 预览改为 40vh 上限自适应展开（不再全部展开）；
  详情面板/卡片编辑/创建页的 SOUL 输入框统一为适中高度 + 可拖拽

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend-web/src/components/workspace/agents/agent-card.tsx

@@ -921,7 +921,7 @@ export function AgentCard({ agent, layout = "card", onPublisherClick }: AgentCar
                     ? "正在加载 SOUL.md..."
                     : "输入 SOUL.md 内容"
                 }
-                className="min-h-[40vh] resize-y font-mono text-xs"
+                className="max-h-[45vh] min-h-48 resize-y font-mono text-xs"
               />
             </div>
             <div className="space-y-2">

frontend-web/src/components/workspace/agents/agent-detail-panel.tsx

@@ -577,13 +577,13 @@ export function AgentDetailPanel({
                 setDraft({ ...draft, soul: e.currentTarget.value })
               }
               placeholder="输入 SOUL.md 内容"
-              className="min-h-[45vh] resize-y font-mono text-xs"
+              className="max-h-[45vh] min-h-48 resize-y font-mono text-xs"
             />
           ) : (
-            // No inner max-height: the SOUL text flows at full length and the
-            // panel body scrolls as a whole, instead of a small nested scroll
-            // box on an otherwise empty screen.
-            <p className="text-muted-foreground whitespace-pre-wrap text-sm leading-relaxed">
+            // Viewport-relative cap: the SOUL preview expands with the screen
+            // (taller than the old fixed 240px box) but never swallows the
+            // whole panel — long content still scrolls inside.
+            <p className="text-muted-foreground max-h-[40vh] overflow-y-auto whitespace-pre-wrap text-sm leading-relaxed">
               {soulPreview}
             </p>
           )}

frontend-web/src/core/threads/hooks.ts

@@ -841,6 +841,47 @@ export function useThreadsPage(options: {
   });
 }
 
+/**
+ * Total number of conversations matching the same filters as
+ * `useThreadsPage`, via the lightweight `/threads/count` endpoint — powers
+ * the "共 N 条 / X 页" display without fetching any rows. Depends only on the
+ * filters (not the page), so paging doesn't refire it.
+ */
+export function useThreadsCount(options: {
+  search?: string;
+  metadata?: Record<string, unknown>;
+}) {
+  const normalizedSearch = options.search?.trim() ?? "";
+  return useQuery<number>({
+    queryKey: [
+      "threads",
+      "search",
+      "count",
+      normalizedSearch,
+      options.metadata ?? null,
+    ],
+    queryFn: async () => {
+      const response = await apiFetch(
+        `${getLangGraphBaseURL()}/threads/count`,
+        {
+          method: "POST",
+          headers: { "Content-Type": "application/json" },
+          body: JSON.stringify({
+            metadata: options.metadata ?? {},
+            query: normalizedSearch || undefined,
+          }),
+        },
+      );
+      if (!response.ok) {
+        throw new Error("Failed to count conversations");
+      }
+      const data = (await response.json()) as { total: number };
+      return data.total;
+    },
+    refetchOnWindowFocus: false,
+  });
+}
+
 export function useDeleteThread() {
   const queryClient = useQueryClient();
   const apiClient = getAPIClient();

frontend-web/src/pages/ChatsPage.tsx

@@ -22,6 +22,7 @@ import {
 } from "@/components/workspace/workspace-container";
 import { useI18n } from "@/core/i18n/hooks";
 import {
+  useThreadsCount,
   useThreadsPage,
   useToggleThreadFavorite,
   useToggleThreadPin,
@@ -90,6 +91,10 @@ export default function ChatsPage() {
     search: debouncedSearch,
     metadata: pinnedFilter,
   });
+  const { data: totalCount } = useThreadsCount({
+    search: debouncedSearch,
+    metadata: favoriteFilter,
+  });
 
   const pinnedThreads = pinnedData?.threads ?? [];
   const pagedThreads = useMemo(
@@ -98,6 +103,10 @@ export default function ChatsPage() {
   );
   const currentPage = page;
   const hasMore = pageData?.hasMore ?? false;
+  // Page windows are sliced over the raw (pinned-inclusive) row order, so the
+  // page count derives from the raw total as well.
+  const totalPages =
+    totalCount != null ? Math.max(1, Math.ceil(totalCount / PAGE_SIZE)) : null;
 
   const renderThread = (thread: AgentThread) => {
     const pinned = isThreadPinned(thread);
@@ -201,6 +210,11 @@ export default function ChatsPage() {
               value={search}
               onChange={(e) => setSearch(e.target.value)}
             />
+            {totalCount != null && (
+              <div className="text-muted-foreground w-full max-w-(--container-width-md) text-right text-xs tabular-nums">
+                共 {totalCount} 条对话
+              </div>
+            )}
           </header>
           <main className="min-h-0 flex-1">
             <ScrollArea className="size-full py-4">
@@ -231,7 +245,9 @@ export default function ChatsPage() {
                       {t.chats.prevPage}
                     </Button>
                     <span className="text-muted-foreground text-sm tabular-nums">
-                      {currentPage}
+                      {totalPages != null
+                        ? `${currentPage} / ${totalPages}`
+                        : currentPage}
                     </span>
                     <Button
                       variant="outline"

frontend-web/src/pages/NewAgentPage.tsx

@@ -546,7 +546,7 @@ export default function NewAgentPage() {
                     placeholder="写下智能体的人设、边界、工作方式和输出要求"
                     value={soulInput}
                     onChange={(event) => setSoulInput(event.currentTarget.value)}
-                    className="min-h-[45vh] resize-y overflow-y-auto font-mono text-xs"
+                    className="max-h-[50vh] min-h-64 resize-y overflow-y-auto font-mono text-xs"
                   />
                 </div>