fix(docs): install Sphinx 9 compatible toolbox

Author: aryanputta

cuda_pathfinder/pixi.toml

@@ -55,6 +55,7 @@ docs = { features = ["docs"], solve-group = "docs" }
 
 [feature.docs.pypi-dependencies]
 nvidia-sphinx-theme = "*"
+sphinx-toolbox = ">=4.2.0"
 
 # TODO: check if these can be extracted from pyproject.toml
 [package]