Show Information that something was written in a Thread in the Main Room

### Your use case

#### What would you like to do?
When you get a notification for a thread there should be an information in the Main Room and when you click on it you get to the thread.

#### Why would you like to do it?
I think threads are confusing for some people.
You have a Notification for a room and when you go into the room there is nothing.
I don't think that all users will conclude that this is because of an event in a Thread.
You have to go to the threads and click onto the right thread to see the message.
I don't think this is user friendly.

#### How would you like to achieve it?
I don't know^^

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

No files, tests, or client entry points are named. Start by clarifying the intended notification and main-room behavior, then identify the relevant Element client implementation. Done means users can recognize that a thread has new activity from the main room and open the correct thread directly.

Written by the indexing model from the issue text.