Threads with new messages don't move to bottom of message timeline

### Steps to reproduce

1. Enter/Create room with a thread that has newer messages after that.
2. Send a message to that thread

### Outcome

#### What did you expect?

The thread moves to the bottom, and in general threads are sorted in the timeline according to their _last_ message, not their first.

#### What happened instead?

The thread is still at the old position, possibly far back in the room history. You need to use the thread list view to find it.

### Operating system

macOS

### Application version

Version von Element: 1.11.104 Krypto-Version: Rust SDK 0.11.0 (404ca47), Vodozemac 0.9.0

### How did you install the app?

https://packages.element.io/desktop/install/macos/Element.dmg

### Homeserver

nitro.chat

### Will you send logs?

No

Reproduce this in the Element desktop app using a room with a thread followed by newer messages, then send a message in that thread. Compare the room message timeline with the thread list view and trace how thread positions are updated. Done means the thread moves to the bottom and ordering follows each thread's last message.

Written by the indexing model from the issue text.