Zen Browser CSS is not being created

### Compositor

- [x] Niri
- [ ] Hyprland
- [ ] MangoWC (dwl)
- [ ] Sway

### Distribution

- [ ] Arch Linux
- [ ] CachyOS
- [x] Fedora
- [ ] NixOS
- [ ] Debian
- [ ] Ubuntu
- [ ] Gentoo
- [ ] OpenSUSE
- [x] Other (specify below)

### If Other, please specify

Fedora Asahi

### dms version

1.2.1

### Description

Even though the zen browser toggle is enabled in themes, the CSS to apply the colors is not created.

### Expected Behavior

The CSS for the Zen Browser theme should be created

### Steps to Reproduce & Installation Method

1. Install zen browser
2. Toggle the zen browser button on themes
3. The CSS for Zen is not there, only the firefox one.

### Error Messages/Logs

_No response_

### Screenshots/Recordings

_No response_

Start at the Themes toggle described in the issue and trace the path that generates browser CSS. Compare the existing Firefox output with the expected Zen Browser output, then reproduce the three listed steps with Zen installed. Done means enabling the Zen toggle creates the CSS and applies the theme colors.

Written by the indexing model from the issue text.