room.getUnreadNotificationCount() always return undefined

I want to get unread chat messages count (total or one room)，but haven't find the right function.

Start by locating room.getUnreadNotificationCount() and tracing how unread message counts are exposed for a room or across rooms. Compare the function's behavior with existing SDK APIs and tests, if present; done means the requested room-level or total unread count is returned consistently rather than undefined.

Written by the indexing model from the issue text.