Collateral Haircut Engine (Basel CRE22)

Basel CRE22 comprehensive-approach collateral haircut engine for counterparty credit risk: applies a caller-supplied, versioned supervisory haircut table (policy input, not hardcoded) to each collateral item's asset class and maturity bucket, scales for a non-standard holding period via the square-root-of-time rule, adds an FX-mismatch haircut where collateral currency differs from exposure currency, and computes net exposure. An item haircut override without a reason code is flagged deficient — the item-level basis for a separate signed human-accountability override record, not minted here. Deterministic per-item haircut application and summation only; no collateral-to-exposure allocation or optimization solver. Evidence artifact only; never a capital-return filing, never regulator-submittable.