Add test to validate markdown files referenced in mkdocs.yml

[sushmanthreddy]

Add test to validate markdown files referenced in mkdocs.yml

This PR adds a test to ensure all markdown files referenced in the navigation section of mkdocs.yml exist in the docs directory. This helps prevent broken links and ensures documentation integrity.

Changes:

• Added new test test_nav_files_exist that:
  • Parses mkdocs.yml to extract markdown file paths
  • Verifies each file exists in docs/docs directory
  • Provides clear error message for any missing files

The test helps catch:

• Typos in file paths
• Missing documentation files
• Incorrect file references

Test location: tests/docs/test_mkdocs_links.py