Desmos: Tutorial Unthemed

### 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 ### Description The tutorials are unthemed. ### Relevant screenshots <img width="275" height="86" alt="Image" src="https://github.com/user-attachments/assets/a79333d6-0e7f-408d-ad85-c10c764ed893" /> ### Browser version(s) this issue occurs on Zen v1.19.9b ### Stylus extension version Stylus 2.3.19 ### Installed version of the userstyle v2026.04.20 ### Any additional comments? Reproduction: 1. Go [here](https://www.desmos.com/calculator) 2. Click the help icon: <img width="33" height="28" alt="Image" src="https://github.com/user-attachments/assets/56c1d400-e234-4a6c-9e90-a60bdff281cc" /> 3. Select any of these: <img width="291" height="85" alt="Image" src="https://github.com/user-attachments/assets/ae3339d2-f49b-4b23-9c1b-1d0da9938fc7" />