//! Layer 3: Algorithms
//!
//! # Purpose
//!
//! This layer implements the core logic for local weighted regression, robustness
//! iterations, and interpolation. It contains the "business logic" of LOESS
//! but is orchestrated by the engine layer.
//!
//! # Architecture
//!
//! ```text
//! Layer 7: API
//! ↓
//! Layer 6: Adapters
//! ↓
//! Layer 5: Engine
//! ↓
//! Layer 4: Evaluation
//! ↓
//! Layer 3: Algorithms ← You are here
//! ↓
//! Layer 2: Math
//! ↓
//! Layer 1: Primitives
//! ```
/// Local weighted regression implementations.
/// Robustness weight updates for outlier downweighting.
/// Interpolation utilities.