Tighten behavioral parity and Simulink validation

[iahncajigas]

Summary

• improve native CIF and network simulation fidelity against the MATLAB help workflows
• add optional MATLAB Engine reference hooks and new simulator/workflow regression tests
• strengthen notebook CI with changed-notebook execution and updated parity audits/reports

Verification

• pytest -q tests/test_workflow_fidelity.py tests/test_simulators_fidelity.py tests/test_matlab_reference.py tests/test_notebook_changed_topics.py tests/test_notebook_ci_groups.py tests/test_notebook_parity_notes.py tests/test_notebook_fidelity_audit.py tests/test_simulink_fidelity_audit.py tests/test_parity_report.py
• python tools/notebooks/run_notebooks.py --group full --topics NetworkTutorial,PPSimExample --timeout 1200