Type Alias DotBatch4Kernel 

pub type DotBatch4Kernel = fn(&[f32], &[f32], &[f32], &[f32], &[f32]) -> [f32; 4];

SIMD kernel type for batch-4 f32 dot product.

Signature: (query, c0, c1, c2, c3) → [dot(q,c0), dot(q,c1), dot(q,c2), dot(q,c3)]. All slices must have equal length (enforced by dot_product_batch4).