docs(sbom): expose reviewer route contract

[stacknil]

Summary

• add the reviewer route contract check to the SBOM reviewer path
• link the route validator from the SBOM reviewer docs
• require the validator link and command in the reviewer route contract

Validation

• python scripts/validate-reviewer-routes.py
• git diff --check
• python scripts/regenerate-example-artifacts.py --check
• python -m pytest tests/test_example_artifacts.py tests/test_provenance_reporting.py tests/test_scorecard_reporting.py

Privacy / security

• checked changed docs and validator for local paths, school identifiers, and secret-like strings