feat(backthink): 后台思考面板并入已存记录——不再只读WS实时事件

后台思考页此前只读 /ws/chat 的 backthink/thinking WS 实时事件(后台任务完成才有)，DB里
270 条 backthink_records 看不到。新增 adminBackthink() 拉 GET /api/v1/admin/backthink +
useAutoReload(10s)，与 WS 事件按 id 去重、按 at 倒序展示；空态/数据源说明更新。
验收: npm run build 99模块全绿

frontend/web/src/admin/modules/Backthink.tsx

@@ -6,6 +6,9 @@ import { Button, EmptyState, Surface, Tag } from "../../components/primitives";
 import type { BackthinkItem } from "../../lib/types";
 import { Icon } from "../../components/Icon";
 import { FlowGraphView } from "./FlowGraph";
+import { adminBackthink } from "../../lib/api";
+import { useAsyncData } from "../../lib/useAsyncData";
+import { useAutoReload } from "../hooks";
 
 function BackthinkRow({ item }: { item: BackthinkItem }): React.ReactNode {
   const markPushed = useAppStore((s) => s.markBackthinkPushed);
@@ -54,12 +57,20 @@ export function BackthinkModule(): React.ReactNode {
   const log = useAuditStore((s) => s.log);
   const [filter, setFilter] = useState<"all" | "notify" | "silent">("all");
   const [interveneHint, setInterveneHint] = useState(false);
-
-  const items = backthink.filter((b) => {
-    if (filter === "notify") return b.shouldNotify === true;
-    if (filter === "silent") return b.shouldNotify !== true;
-    return true;
-  });
+  // Persisted records (design/12 §4) + live WS backthink events, deduped by id,
+  // newest first. The panel previously only showed live WS events and hid history.
+  const rec = useAsyncData(() => adminBackthink(100), []);
+  useAutoReload(rec.reload, 10000);
+  const byId = new Map<string, BackthinkItem>();
+  for (const b of backthink) if (b.id) byId.set(b.id, b);
+  for (const b of rec.data ?? []) if (b.id) byId.set(b.id, b);
+  const items = Array.from(byId.values())
+    .sort((a, b) => (b.at ?? 0) - (a.at ?? 0))
+    .filter((b) => {
+      if (filter === "notify") return b.shouldNotify === true;
+      if (filter === "silent") return b.shouldNotify !== true;
+      return true;
+    });
 
   return (
     <div className="space-y-5">
@@ -99,7 +110,7 @@ export function BackthinkModule(): React.ReactNode {
         </div>
       )}
 
-      <Notice>数据源：/ws/chat 下行 backthink / thinking 与 graph_update 事件（实时）。干预为后端 M10+ 提供，当前为只读展示。</Notice>
+      <Notice>数据源：GET /api/v1/admin/backthink（已存记录，每 10s 刷新）+ /ws/chat 下行 backthink / thinking 与 graph_update 事件（实时）合并去重。干预为后端 M10+ 提供，当前为只读展示。</Notice>
     </div>
   );
 }

frontend/web/src/lib/api.ts

@@ -14,6 +14,7 @@ import type {
   ApiErrorShape,
   ApiKeyIssueResult,
   AuditRecord,
+  BackthinkItem,
   AutomationCreateResult,
   AutomationRunResult,
   ChannelTestResult,
@@ -683,3 +684,8 @@ export function adminObservabilityAudit(limit?: number): Promise<AuditRecord[]>
 function limitQuery(limit?: number): string {
   return limit && limit > 0 ? `?limit=${limit}` : "";
 }
+
+/** GET /api/v1/admin/backthink — persisted background-think records (newest first). */
+export function adminBackthink(limit?: number): Promise<BackthinkItem[]> {
+  return request<BackthinkItem[]>(`/admin/backthink${limitQuery(limit)}`);
+}