Provide more control over unread dot state

### Your use case

#### What would you like to do?

I'm in a high-traffic chat room in which I only occasionally get `@`-mentioned. I have the notification for that room set to `Mentions & keywords`. Yet, I still get the unread dot marker shown next to the room name each time a message is posted there. I really don't want to see the unread marker, unless I get mentioned.

#### Why would you like to do it?

Having unread markers shown for situations someone isn't interested in getting notified is not effective, as it draws attention without function.

#### How would you like to achieve it?

Don't show the unread marker unless mentioned or keyworded.

### Have you considered any alternatives?

Muting the room, but then I don't get notified when I need to

### Additional context

_No response_

Start by checking how Element clients distinguish room notifications from unread dot markers when a room is set to “Mentions & keywords.” Confirm the behavior across the relevant client surfaces; done means ordinary messages do not show the marker, while mentions or keywords still do and notifications remain available.

Written by the indexing model from the issue text.