Desmos: Line Regression Option is Part Light Part Dark

### Is there an existing issue outlining your problem?

- [x] I have searched the existing issues and they do not solve my problem.

### What userstyle are you seeing the problem on?

lbl:desmos

### Describe your problem.

The line regression icon is strange. The line is dark but the dots are light. They line and dots should be the same dark colour: base.

### Attach screenshots.

[desmos.png](https://github.com/user-attachments/assets/5f35525c-1dbd-4fea-9507-22832ff09c59)

### Browser version(s) this issue occurs on

Zen v1.19.8b

### Stylus extension version

Stylus 2.3.19

### Installed version of the userstyle

v2026.04.20

### Any additional comments?

The dots are light because of this:
```css
@media (prefers-color-scheme: dark) {
:root i:not(.dcg-shared-product-icon, .dcg-icon-error, .dcg-geo-basic-tools .dcg-icon-caret-down, .dcg-geometry-toolbar-view i, .dcg-btn-short-blue i) {
opacity: 1 !important;
text-shadow: none !important;
color: #cdd6f4 !important;
}
}
```
(from the userstyle)

Locate the lbl:desmos userstyle and inspect the dark-mode selector shown in the issue. Check how it affects the line regression icon, then adjust the styling so the line and dots use the same dark base color and verify the icon in Desmos dark mode.

Written by the indexing model from the issue text.