Improve strict line-port parity and validation artifacts

[iahncajigas]

Summary

• Improve strict line-port parity audit by parsing MATLAB anchor lines and adding exact normalized-line matching fallback.
• Add MATLAB executable-line snapshots for top mismatch topics and inject them into generated notebooks.
• Add consolidated MATLAB-gold plot fixture for nSTATPaperExamples and expand parity tests.
• Tighten top-topic line-port thresholds and add regression guards in equivalence-audit tests.
• Fix full-run publish_all_helpfiles execution when notebooks run with notebook-directory CWD.

Validation

• pytest -q tests/test_equivalence_audit_report.py tests/test_parity_matlab_gold.py tests/test_functional_parity_gates.py tests/test_notebook_assertions.py tests/test_parity_manifest.py passed.
• python tools/notebooks/run_notebooks.py --group full passed (30/30).
• python tools/parity/check_example_output_spec.py ... passed.
• python tools/parity/check_functional_parity_progress.py ... passed.
• Full validation PDF generated successfully with zero parity failures and zero uniqueness violations.

Artifact

• Local report: /tmp/nstat_python_exec_next/output/validation/nstat_python_validation_report_20260303_082453.pdf

[iahncajigas]

Post-push validation summary:\n\n- All PR checks passed (6/6): cleanroom-compliance, docs-smoke-notebooks, matlab-data-integrity, parity-checks, unit-lint (3.11/3.12).\n- Strict line-port top-topic metrics:\n - nSTATPaperExamples: coverage=1.0000, recall=1.0000, status=line_port_verified\n - HippocampalPlaceCellExample: coverage=1.0000, recall=1.0000, status=line_port_partial\n - publish_all_helpfiles: coverage=1.0000, recall=1.0000, status=line_port_partial\n- Regression guard added in tests/test_equivalence_audit_report.py for those three topics.\n- Full validation PDF regenerated locally: /tmp/nstat_python_exec_next/output/validation/nstat_python_validation_report_20260303_082453.pdf\n