/// One nearest-neighbor result. Lower distance is better.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct SearchHit {
/// Stable caller-provided vector key.
pub key: u64,
/// Distance under the configured metric. Cosine is in `0.0..=2.0`,
/// squared Euclidean is non-negative, and dot distance is the negative
/// inner product.
pub distance: f32,
}