v0.8.0 — Phase 9: abstention & calibration
The system knows what it doesn't know, measurably.
- Gate 1 RetrievalGate: abstain on low retrieval confidence (top score + top-1/top-k margin), before generation.
- Gate 2 answerability classifier: Polaris pair head (num_classes=2) over the question + top passages.
- Risk–coverage: risk_coverage_curve / operating_point (~80% coverage target, ADR-0007). Off-domain/personal-advice questions abstain.