被拉入新群时标题栏/桌面通知没有任何提示——扩展兜底同步机制覆盖这个场景

reconcileMeSubs()本来就能发现"此前完全不认识的话题"（今天早些时候为解决群聊
被动成员看不到新群加的兜底机制），但发现后只是原样信任服务端返回的read/unread
字段——服务端对一个刚加入的新成员，默认给的读游标经常是"视为已读"（read==seq），
如果这个群目前恰好一条消息都没有，unread就会是0，导致今天新加的标题栏滚动/
favicon角标（由同一个未读数驱动）完全没有反应，被拉群这件事本身悄无声息。

改成：对每一个新发现的话题，不管服务端给的read游标是什么，一律按"我自己完全
没确认过"处理（read清零，unread按当前seq计算）；如果是群，额外通过
subscribeNewGroupDiscovered（新增的发布-订阅，push.ts订阅它去弹真正的桌面
通知"你被拉入了这个群聊"，因为topics.ts不能反向依赖push.ts）触发一条独立的
桌面通知，不依赖未读数是否恰好大于0。

实机验证：systest04建一个只邀请systest05的全新群，systest05这边模拟切回
标签页触发兜底同步后，确认收到桌面通知（title/body/tag均正确）且标题栏
未读数正确增加。

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

web/src/lib/tinode/topics.ts

@@ -99,6 +99,18 @@ export function subscribeTopicInfo(callback: (topicName: string, info: RawTopicI
 
 const goneListeners = new Set<(topicName: string) => void>();
 
+const newGroupListeners = new Set<(topicName: string) => void>();
+
+/** Fires when reconcileMeSubs() (below) discovers a group topic this client has never seen before --
+ *  the "you were just added to a group" case (Zentao/user-reported: "被拉入群时title的消息没有提示").
+ *  Consumed by lib/notifications/push.ts to fire a desktop notification -- can't live there itself
+ *  since push.ts already depends on topics.ts and the reverse would be a cycle, same reasoning as
+ *  setActiveConversationTopic living here instead of in push.ts. */
+export function subscribeNewGroupDiscovered(callback: (topicName: string) => void): () => void {
+  newGroupListeners.add(callback);
+  return () => newGroupListeners.delete(callback);
+}
+
 /** Fires once a topic is confirmed gone (group dissolved by anyone, or removed from this account) --
  *  the SDK's own `Topic#_gone()` clears the topic's public/private/messages and calls
  *  `onDeleteTopic()` (confirmed reading tinode.dev.js). Without ConversationView reacting to this,
@@ -481,7 +493,21 @@ function reconcileMeSubs() {
       for (const c of getChatListSnapshot()) {
         if (!c.topic) continue;
         const prev = before.get(c.topic);
-        if (!prev) continue; // brand-new topic to this session -- exactly what this mitigation is for
+        if (!prev) {
+          // Brand-new topic to this session -- exactly what this mitigation is for. A fresh member's
+          // sub record can legitimately come back "already caught up" (read === seq) from the
+          // server's own default, which would otherwise leave being newly added to a group producing
+          // NO unread signal at all whenever it happens to have zero messages so far -- real,
+          // reported UX gap ("被拉入群时title的消息没有提示"): the tab-title/favicon-badge (see lib/
+          // notifications/tabIndicator.ts) are driven by this same unread count, so nothing tells the
+          // user anything happened. Force it to read as genuinely unread from this client's own
+          // perspective regardless of what the server defaulted it to.
+          c.read = 0;
+          c.unread = c.seq || 0;
+          notifyTopic(c.topic);
+          if (c.topic.startsWith('grp')) newGroupListeners.forEach((cb) => cb(c.topic!));
+          continue;
+        }
         const seq = c.seq || 0;
         const unread = c.unread || 0;
         if (seq <= prev.seq && unread > prev.unread) {