New thread replies not showing up in thread list right-panel

### Steps to reproduce

1. View a room
1. Open the threads list
1. Notice a thread I replied to yesterday still shows my message as the preview (no activity indicator). Other new threads have activity
1. Click on the thread in question
1. Notice a new reply actually shows up
1. Going back to the thread list shows the new message as the preview now

Keep in mind, the new activity occurred while I was offline but my client wasn't trying to fetch anything and would never have indicated something was there unless I clicked on it.

Before clicking on thread | After clicking on thread | Thread
--- | --- | ---
| |

---

Reproduced again on 2026-07-02

### Outcome

#### What did you expect?

The list of threads should show new activity for all threads in the room.

If the client hasn't caught up, then it should show an indeterminate state on the thread (perhaps loading indicator). In this case, I don't think the client was trying to catch up at all though but it should still indicate that it's not sure yet whether there are new replies. The client should back paginate all history to ensure nothing is being left in the gaps.

#### What happened instead?

Only some old message in the preview is shown which makes it seem like there is nothing new in the thread to catch up on :feelsgood:

### Operating system

Manjaro Linux (Arch-based)

### Browser information

Chrome Version 145.0.7632.116

### URL for webapp

develop.element.io

### Application version

Element version: e58e80336829-js-fd01b172368e Crypto version: Rust SDK 0.16.0 (1ac734e), Vodozemac 0.9.0

### Homeserver

matrix.org

### Will you send logs?

Yes -> https://github.com/element-hq/element-web-rageshakes/issues/32728

The three events in question are ([permalink](https://matrix.to/#/!SGNQGPGUwtcPBUotTL:matrix.org/$Tgpmf70G5psb8ihD_UJzbJ-LX-5aSpirabKws64LNr0?via=jki.re&via=element.io&via=matrix.org)):

- Room ID: `!SGNQGPGUwtcPBUotTL:matrix.org`
- Thread root: `$Tgpmf70G5psb8ihD_UJzbJ-LX-5aSpirabKws64LNr0`
- Thread reply 1: `$k8sBLQEXrNOslCgFpqXVaHdB4jqDSDMcKTE9ZLUs8qU`
- Thread reply 2: `$xpB55ucWYBNEG_pbADUbvLV2O_McG6fphCi9ZK3gIrU`