Threads: Open right panel thread list by default if unread notifications

### Your use case

We're hearing feedback that threads are easy to miss or hard to find.
What if we opened the right panel by default if you went into a room that had unread notifications?

I'm not sure how this would play out if you have the right panel open labs flag on...

WDYT?

(This was a suggestion in the Daily Mobile room today)

### Have you considered any alternatives?

_No response_

### Additional context

_No response_