feat(backthink): 后台思考页接 WS 实时——ws.ts 处理 backthink 事件头插 store

后端每次思考落库发 ws.backthink(bus→hub→WS)，此前 ws.ts 无 case、addBackthink 是死方法。
新增 case `backthink`→parseBackthinkItem→s.addBackthink 头插；parseBackthinkItem 兼容
Go默认字段(ID/Trigger/At/Conclusion/ShouldPush/PushResult)与admin camelCase。
配合页面(行key=id)实现增量插入、不整页重渲。build 99模块绿。

frontend/web/src/lib/ws.ts

@@ -5,6 +5,7 @@ import {
   parseAdminChannelMessage,
   parseAgent,
   parseAwakenTool,
+  parseBackthinkItem,
   parseGraph,
   parsePersistedMessage,
   parseTool,
@@ -95,6 +96,14 @@ function dispatch(ev: { type: string; data: unknown }): void {
       if (msg) s.pushChannelEvent(msg);
       break;
     }
+    case "backthink": {
+      // design/12 §4 — a background-think pass result was persisted. Head-insert into
+      // the store so the admin backthink panel appends it in realtime (rows keyed by
+      // id → React reconciles incrementally, no whole-page re-render).
+      const item = parseBackthinkItem(r);
+      if (item) s.addBackthink(item);
+      break;
+    }
     case "thinking.start": {
       pendingThinking = "";
       break;

frontend/web/src/lib/wsParse.ts

@@ -1,4 +1,4 @@
-import { MODES, type AdminChannelMessage, type AgentInfo, type ChatMessage, type FlowGraph, type Mode, type ToolUsed } from "./types";
+import { MODES, type AdminChannelMessage, type AgentInfo, type BackthinkItem, type ChatMessage, type FlowGraph, type Mode, type ToolUsed } from "./types";
 import { now, uid } from "./util";
 
 /**
@@ -183,3 +183,27 @@ export function parseAdminChannelMessage(v: unknown): AdminChannelMessage | null
     createdAt: typeof r.createdAt === "number" ? r.createdAt : now(),
   };
 }
+
+/** Decode a background-think `backthink` WS payload into a BackthinkItem. The bus
+ * publishes the raw `backthink.Record` (Go default field names ID/Trigger/At/
+ * Conclusion/ShouldPush/PushResult); the admin wire uses camelCase, so this reads
+ * both defensively and returns null when the id cannot be resolved. */
+export function parseBackthinkItem(v: unknown): BackthinkItem | null {
+  const r = toRecord(v);
+  if (!r) return null;
+  const idRaw = r.ID ?? r.id ?? r.record_id ?? r.recordId;
+  if (idRaw === undefined || idRaw === null) return null;
+  const atRaw = r.At ?? r.at;
+  let at = 0;
+  if (typeof atRaw === "number") at = atRaw;
+  else if (typeof atRaw === "string") {
+    const t = Date.parse(atRaw);
+    if (!Number.isNaN(t)) at = t;
+  }
+  const trigger = typeof r.Trigger === "string" ? r.Trigger : typeof r.trigger === "string" ? r.trigger : "";
+  const conclusion = typeof r.Conclusion === "string" ? r.Conclusion : typeof r.conclusion === "string" ? r.conclusion : "";
+  const pr = toRecord(r.PushResult) ?? {};
+  const shouldNotify = (r.ShouldPush ?? r.shouldNotify ?? r.should_push) === true;
+  const pushed = (pr.Pushed ?? pr.pushed ?? r.pushed ?? r.push_pushed) === true;
+  return { id: String(idRaw), trigger, conclusion, shouldNotify, pushed, at };
+}