↑ doesn't work for quick-edit in threads

[poolcritter]

Describe the bug

Normally, ↑ works in root rooms to quickly edit the last-sent event. This is not true for the thread sidebar.

Reproduction

1. Create a message event
2. Create a message event that thread-replies to the previous event
3. Open the thread sidebar and create a message event from there
4. Attempt to press ↑ to edit it

Expected behavior

↑ should edit the last message event authored by you in the thread.

Platform and versions

- OS: Linux x86_64
- Browser: Mozilla/5.0 (X11; Linux x86_64; rv:140.0) Gecko/20100101 Firefox/140.0
- Sable: v1.11.1-dev (476ec6f)

Additional context

No response