test(ci): add unit tests for documentation link validation (#2186)

[Sneha-Anand1910]

Description

This PR adds unit tests for the documentation link validator (scripts/validate_doc_links.py). The script had no tests, so this adds coverage to make sure it reliably catches broken documentation links before they reach CI.

Related Issues

Fixes #2186

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Added a new test file testing/backend/unit/test_validate_doc_links.py with 5 tests covering:

• a valid relative link with a valid anchor (passes cleanly)
• a link to a missing file (reports a broken link target)
• a link with a broken #anchor (reports the anchor as not found)
• external / in-page / mailto links (correctly skipped)
• slugify producing GitHub-style anchors

Run locally with:
python -m pytest testing/backend/unit/test_validate_doc_links.py -v

Result: all 5 tests pass.

Checklist

• My code follows the code style of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.

[Sneha-Anand1910]

Hi @utksh1 , I've addressed the requested changes and pushed the latest updates. Please let me know if there's anything else I should modify. Thank you!

[utksh1]

Reviewed the focused test change and its current checks are green. The PR still needs a current branch update before merge because it is behind main; I will not bypass the branch policy.

[Sneha-Anand1910]

Hi @utksh1, thanks for the approval! Branch is updated with main. This PR only adds a Python test and touches no frontend code, so the failing frontend checks look unrelated (likely pre-existing). I can't re-run from my fork , could you re-run them when you get a chance?