//! `aura-core` — the shared contract every aura component links against.
//!
//! This crate is the boundary forced by the cdylib hot-reload model: both the
//! engine and every hot-reloadable node cdylib depend on it, so it must stay
//! small and stable. It is the home of (to be specified):
//!
//! - the scalar base types streamed as SoA: `i64`, `f64`, `bool`, `timestamp`;
//! - the `Node` trait — the contract an authored node implements (`schema` +
//!   `eval`), with engine-provided read-only input windows and node-internal
//!   series;
//! - the evaluation context `Ctx` (zero-copy indexed access into input columns,
//!   fresh-mask, current-cycle timestamp);
//! - the firing-policy declarations (A: fire-on-any-fresh + hold; B: all-fresh
//!   barrier), declarable per input group.
//!
//! Types are intentionally absent until the first spec lands under
//! `docs/specs/`. This crate documents intent; it does not yet define API.