Fix joke-grading false positives and silent KB data loss

Add parallel LangChain RAG engine; harden pipeline from architecture audit

Fix sentinel edge cases: hallucination combo guard + UI formatting

Replace ad-hoc refusal regexes with NOT IN DOCUMENTS sentinel

Fix refusal detector missing 'not able to' and 'outside scope' phrases

Replace HHEM with sentence-level NLI, add claim decomposition and drift detection

Add typed client library, unit + integration tests, mypy, ruff, NOTES.md