Enterprise-ready demo: schemas, scoring, features, tests

[MadhurKh]

PR Summary

• Added strict schemas + data/model contracts for DS ↔ Eng handshake
• Added feature extraction layer + scoring breakdown for explainability
• Added unit tests to protect interface stability
• Streamlit UI updated to show Risk Register, Evidence, Features, Scoring, Audit, Download JSON

How to review

• Run: py -m streamlit run streamlit_ui/dashboard.py
• Run tests: py -m pytest -q

Why it matters

• Enables DS iteration (rules/LLM/ML) behind a stable adapter boundary without UI changes.