Function dense_gemv_fp8w 

pub fn dense_gemv_fp8w(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight: &Fp8DenseWeight,
    output: DevicePtr,
    n: u32,
    k: u32,
    stream: u64,
) -> Result<()>

2026-09-25: FP8-weight GEMV for one row, C = A @ (dequant(B_fp8) * row_scale)^T: A [1, K] BF16, B [N, K] FP8 E4M3, row_scale [N] f32, C [1, N] BF16. One byte per weight, against two for dense_gemv. Each 256-thread block computes 4 outputs, 64 threads per output (kernel dense_gemv_fp8w(A, B, row_scale, C, N, K)).