Function moe_router_gemm 

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

2026-09-26: The MoE router gate GEMM, C = A @ B^T with the operands of dense_gemm and its bits (kernel moe_router_gemm_bf16): each output keeps one FP32 accumulator over k = 0..K-1 in order, but a block stages a 512-wide K slice of 4 weight rows and up to 16 activation rows in shared memory at once instead of waiting on every 16-wide tile. k must be a multiple of 16 (below that dense_gemm adds zero padding terms).