Tighten source-driven analysis and notebook audit parity

[iahncajigas]

Summary

• align canonical Analysis deviance/AIC/BIC behavior more closely with MATLAB and add MATLAB-backed analysis fixtures
• regenerate notebook/report audits from source, including honest partial status for StimulusDecode2D and expanded Simulink inventory
• update helpfile notebook builders and MATLAB reference tests for the new audit and fixture coverage

Verification

• pytest -q
• python tools/notebooks/run_notebooks.py --group helpfile_full --topics TrialExamples,ValidationDataSet,StimulusDecode2D --timeout 1800
• python tools/parity/export_matlab_gold_fixtures.py