Speakers can still be stuck off-screen

### Steps to reproduce

1. Be in spotlight layout in a large meeting watching a screen share
2. Have various people talk
3. ???

### Outcome

#### What did you expect?

Whoever's speaking should always appear on screen in the column on the right.

#### What happened instead?

> valere: X was talking, but he was 10 on the list on the right, so could not see him
> valere: lots of polish on huddles :D
> Robin: Was he scrolled off the bottom of the screen?
> valere: yes way off
> valere: Y is also out of screen for me
> Robin: I see, that's not expected
> valere: switching layout did help

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

Hostname: call.pro.element.io Element Call version: v0.16.1

### Will you send logs?

No

Reproduce the issue at call.pro.element.io in spotlight layout while watching a screen share and having several people speak. Start by tracing the right-hand speaker column and its scrolling or active-speaker behavior; done means the current speaker remains visible in that column without switching layouts.

Written by the indexing model from the issue text.