UX: fix channel name style for unread threads (#30152)

Follow up to #30127.

Normally when viewing a channel with tracked threads, we dismiss the blue dot next to the channel name even though the thread has not been read yet.

This change applies the same criteria to determine if we should bold the channel name.

plugins/chat/assets/javascripts/discourse/components/chat-channel-row.gjs

@@ -142,7 +142,7 @@ export default class ChatChannelRow extends Component {
   get channelHasUnread() {
     return (
       this.args.channel.tracking.unreadCount > 0 ||
-      this.args.channel.unreadThreadsCount > 0
+      this.args.channel.unreadThreadsCountSinceLastViewed > 0
     );
   }