fix: add update_index.py to deploy workflow

The deploy.yml was missing the update_index.py script call that clone-content.sh
runs locally. This caused the live site to display the master branch README.md
content directly instead of the generated index.md with proper section links.

Author: sntxerror

.github/workflows/deploy.yml

@@ -123,6 +123,7 @@ jobs:
         run: |
           python scripts/update_sections_nav.py
           python scripts/update_nav.py
+          python scripts/update_index.py
           
       - name: Build site
         run: mkdocs build