Implement pre-push hook for domain doc validation

[Coldaine]

Following the update to MasterDocumentationPlaybook 1.0.1, we need to implement a pre-push hook that runs the naming validator.

• Create/Update scripts/install-githooks.sh to set up the hook.
• Ensure the hook calls scripts/validate_domain_docs_naming.py.
• Document installation steps in the repo README or dev docs.

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.