Game embed only works in floating mode when overriding with override.cfg

### Tested versions

v4.5.1.stable.official [f62fdbde1]

### System information

macOS Tahoe 26.0.1, Forward+

### Issue description

So i was trying to make the game running fullscreen for export but keep it embedded while developing
To do so i specified settings override in `override.cfg`

However, the game always runs as floating window instead of embedding and ignores checkboxes below

### Steps to reproduce

Project Settings > Display > Window > Mode = Fullscreen

`override.cfg`
```
[display]
window/size/mode=0
```

Embed Game on Next Play is checked
Make Game Workspace Floating on Next Play is unchecked

### Minimal reproduction project (MRP)

[new-game-project.zip](https://github.com/user-attachments/files/23509916/new-game-project.zip)

Start with the supplied minimal reproduction project and the override.cfg entry for display/window/size/mode. Reproduce with Embed Game on Next Play enabled and Make Game Workspace Floating on Next Play disabled, then trace how these settings interact with fullscreen mode. Done means the game remains embedded during development while fullscreen export behavior is preserved.

Written by the indexing model from the issue text.