Fix docs build: add cmake and fetch submodules

Author: JDRomano2

.github/workflows/build-docs.yml

@@ -36,6 +36,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           fetch-depth: 0 # Full history for versioning
+          submodules: recursive # Fetch pybind11, pugixml, and other submodules
 
       - name: Set up Python
         uses: actions/setup-python@v5
@@ -45,7 +46,7 @@ jobs:
       - name: Install system dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y doxygen graphviz
+          sudo apt-get install -y doxygen graphviz cmake
 
       - name: Install Python dependencies
         run: |