第五轮深度测试：管理员撤回、所有人@提醒、失效附件UI，并核对现存后端问题清单

- messages-view.jsx: 拖拽发送/回复菜单在编辑态下的旁路修复；群主/管理员可撤回他人消息
  (对齐后端 authorizeIMMessageMutation 的 allowAdmin)；新增"所有人"@提醒(head.mention_all)。
- chat-message.jsx: system_action 头类型消息按 system_notice 同款渲染(此前显示"内容无效")。
- content-library-view.jsx: 语音/链接/图文收藏与聊天记录卡片补上 removed(已失效)态UI，
  之前只有 FileCard 处理了这个状态。
- call-panel.jsx: handleVideoOfferMsg(5步.then链，用reject sentinel跳过后续步骤)、
  handleToggleSpeakerClick 补组件卸载守卫，修完此前遗漏的两处。
- group-management-view.jsx: 治理开关(Governance.setField)和群主转让(OwnerSelect)
  补上乐观锁 version 参数(此前从不传，服务端 version<=0 时会跳过冲突检测)；群文件搜索框
  文案承诺"搜索文件名或者上传者"但服务端q参数只匹配文件名，改为拉取全量列表本地按文件名+
  已解析的上传者昵称一起过滤；群公告详情页补上从未被调用过的已读上报(readGroupAnnouncement)。

以上均用真实账号在浏览器/直接请求验证：管理员撤回、system_action渲染、mention_all、
文件按上传者搜索、公告已读上报(200)、治理开关stale-version探测确认409冲突检测生效。

7个并行测试agent对全部11章做了第二轮回归+现存后端问题清单逐条复核，结论待整理进
docs/IM-后端问题清单*.md（全部现存条目复核后均建议保留，多条证据强度从推断升级为已验证）。

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

umd/src_widgets_call-panel_jsx.dev.js

@@ -31,6 +31,7 @@ CALL_ENDED_SOUND.loop = true;
 const DIALING_SOUND = new Audio('audio/dialing.m4a');
 const VIDEO_MUTED_EVENT = 'video:muted';
 const VIDEO_UNMUTED_EVENT = 'video:unmuted';
+const UNMOUNTED_DURING_OFFER = Symbol('unmounted-during-offer');
 function formatElapsedTime(totalSeconds) {
   const h = Math.floor(totalSeconds / 3600);
   const m = Math.floor(totalSeconds % 3600 / 60);
@@ -498,6 +499,10 @@ class CallPanel extends (react__WEBPACK_IMPORTED_MODULE_0___default().PureCompon
     pc.setRemoteDescription(desc).then(_ => {
       return navigator.mediaDevices.getUserMedia(this.localStreamConstraints);
     }).then(stream => {
+      if (this._unmounted) {
+        stream.getTracks().forEach(t => t.stop());
+        return Promise.reject(UNMOUNTED_DURING_OFFER);
+      }
       let dummyVideo;
       if (!this.localStreamConstraints.video) {
         dummyVideo = this.emptyVideoTrack();
@@ -525,7 +530,11 @@ class CallPanel extends (react__WEBPACK_IMPORTED_MODULE_0___default().PureCompon
       this.setState({
         callInitialSetupComplete: true
       }, _ => this.drainRemoteIceCandidatesCache());
-    }).catch(this.handleGetUserMediaError);
+    }).catch(err => {
+      if (err !== UNMOUNTED_DURING_OFFER) {
+        this.handleGetUserMediaError(err);
+      }
+    });
   }
   handleRemoteHangup() {
     if (!this.state.waitingForPeer) {
@@ -685,10 +694,17 @@ class CallPanel extends (react__WEBPACK_IMPORTED_MODULE_0___default().PureCompon
     navigator.mediaDevices.enumerateDevices().then(devices => {
       const outputs = devices.filter(d => d.kind == 'audiooutput');
       const match = nextOn ? outputs.find(d => /speaker/i.test(d.label)) : outputs.find(d => /earpiece|receiver/i.test(d.label));
+      if (this._unmounted || !this.remoteRef.current) {
+        return null;
+      }
       return this.remoteRef.current.setSinkId(match ? match.deviceId : '');
-    }).then(_ => this.setState({
-      speakerOn: nextOn
-    })).catch(err => console.error('Failed to switch audio output device', err));
+    }).then(_ => {
+      if (!this._unmounted) {
+        this.setState({
+          speakerOn: nextOn
+        });
+      }
+    }).catch(err => console.error('Failed to switch audio output device', err));
   }
   render() {
     const audioTracks = this.state.localStream && this.state.localStream.getAudioTracks();