Site: Fix shaders on site article

There are some inaccuracies in the writing shaders articles. I need to fix that.

Start by locating the site articles about writing shaders, since no file or test is named in the issue. Review the articles for the reported inaccuracies and confirm the work is complete when the affected explanations are corrected and the site content builds or renders successfully.

Written by the indexing model from the issue text.