feat(backthink): 后台思考页全 WS 实时驱动——去掉轮询整页重渲

后端每次思考落库发 ws.backthink → useAppStore.backthink head-insert。页面临近打开时
冷拉一次历史(adminBackthink)，此后靠 WS 事件增量更新；去掉 useAutoReload(10s)轮询替换
数组(会整页重渲)。行 key=id → React 只插入新记录、不动已有行。build 99模块绿。

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

@@ -8,7 +8,6 @@ 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);
@@ -57,10 +56,11 @@ export function BackthinkModule(): React.ReactNode {
   const log = useAuditStore((s) => s.log);
   const [filter, setFilter] = useState<"all" | "notify" | "silent">("all");
   const [interveneHint, setInterveneHint] = useState(false);
-  // Persisted records (design/12 §4) + live WS backthink events, deduped by id,
+  // Cold-load persisted history once (design/12 §4); real-time updates come from the
-  // newest first. The panel previously only showed live WS events and hid history.
+  // WS `backthink` events already feeding useAppStore.backthink (head-inserted), so we
+  // do NOT poll-replace the array (which would re-render the whole list). Rows are keyed
+  // by id → React reconciles incrementally, appending only NEW records.
   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);
@@ -110,7 +110,7 @@ export function BackthinkModule(): React.ReactNode {
         </div>
       )}
 
-      <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>
+      <Notice>数据源：/ws/chat 下行 backthink / thinking 事件（实时，主驱动）+ 打开时一次拉取 GET /api/v1/admin/backthink 历史，两者按 id 去重、按时间倒序，新记录增量插入（不整页重渲）。干预为后端 M10+ 提供，当前为只读展示。</Notice>
     </div>
   );
 }