Function linear_avx2 

pub unsafe fn linear_avx2(
    x: &[f32],
    weight: &[f32],
    bias: &[f32],
    batch: usize,
    in_features: usize,
    out_features: usize,
    output: &mut [f32],
)

AVX2 linear projection – delegates to scalar.

Safety

Requires AVX2 support.