chatgui: fix dual selection highlight and missing online count

- channellist.cpp: selectionChanged guard now checks currentIndex().row()
  is within model->rowCount() to avoid re-selecting stale index after
  model clear, which caused both channels to stay blue when switching.
- chat_sync.c: cs_refresh_channels now posts CHANNEL_PEERS_ONLINE
  for all channels after loading, fixing online count showing only
  on the last connected group.

tools/chatgui/src/channellist.cpp

@@ -56,7 +56,8 @@ protected:
     }
     void selectionChanged(const QItemSelection& sel, const QItemSelection& desel) override {
         QListView::selectionChanged(sel, desel);
-        if (selectionModel() && !selectionModel()->hasSelection() && currentIndex().isValid())
+        if (selectionModel() && !selectionModel()->hasSelection() && currentIndex().isValid()
+            && currentIndex().row() < model()->rowCount())
             selectionModel()->select(currentIndex(), QItemSelectionModel::ClearAndSelect);
     }
 

tools/chatgui/transport/chat_sync.c

@@ -508,6 +508,9 @@ static void cs_refresh_channels(struct chat_sync* cs) {
                 memcpy(&cs->channels[i].peer_ids[j], peer_buf + 2 + j * 8, 8);
         }
     }
+
+    for (int i = 0; i < cs->channel_count; i++)
+        cs_post_channel_online(cs, cs->channels[i].channel_id);
 }
 
 static void refresh_timer_cb(void* arg) {