Function dense_gemm_m16_bf16_n64 

pub fn dense_gemm_m16_bf16_n64(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight: &DenseWeight,
    output: DevicePtr,
    m: u32,
    n: u32,
    k: u32,
    a_row_stride: u32,
    c_row_stride: u32,
    stream: u64,
) -> Result<()>

2026-09-25: The N_TILE = 64 instantiation of the same kernel template: the same arguments as dense_gemm_m16_bf16, ceil(n / 64) CTAs instead of ceil(n / 32).