Threads timeline can be completely misordered.

### Steps to reproduce

1. Click on a long thread in the thread panel to read it. It loads the last N messages of the thread
2. Switch room
3. Switch back again
4. The thread paginates in the previous N messages of the thread, but *appends* them rather than prepends them to the thread timeline - or something similarly whacky. As a result, you end up with the pages out of order for the thread. Switching thread and back again fixes it.

### Outcome

#### What did you expect?

Reliable thread ordering.

#### What happened instead?

Some kind of race between thread-pagination and thread-load which means the old page loads before the new page.

I don't have logs, but will rageshake when it next happens, which is roughly 30% of the time when loading a long thread.

### Operating system

_No response_

### Application version

nightly

### How did you install the app?

_No response_

### Homeserver

_No response_

### Will you send logs?

No