//! FX models — Grzelak–Oosterlee FX-HHW and FX-HLMM (short-rate and
//! Libor-market-model variants of cross-currency Heston), the
//! time-dependent SABR stack (van der Stoep et al., 2015) including
//! effective-parameter mappings, calibration and the particle-method
//! SLV compensator, plus the Dupire local-vol surface that feeds it.
//!
//! Parallels `crate::derivatives::forex` and `crate::markets::forex`.