//! Vector similarity scoring backends.
//!
//! One backend is shipped:
//! - `linear`: SIMD-dispatched linear scan. Best for 10–100 candidate actions.
//!
//! An HNSW ANN backend was scoped and deferred (see M6 deferred-note in the
//! implementation plan). The `VectorBackend` enum in `scoring` keeps it
//! extensible.