Function conv1d_update_prefill 

pub fn conv1d_update_prefill(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    conv1d_prefill_tp_k: KernelHandle,
    conv_state: DevicePtr,
    input: DevicePtr,
    weight: &DenseWeight,
    bias: DevicePtr,
    output: DevicePtr,
    d_inner: u32,
    d_conv: u32,
    seq_len: u32,
    input_stride: u32,
    output_stride: u32,
    stream: u64,
) -> Result<()>

2026-09-25: Conv1d update + SiLU over seq_len prefill tokens, with separate per-token input and output strides. Runs the token-parallel kernel (conv1d_prefill_tp_k) when its handle is non-zero and METRALE_CONV1D_TP is not 0, else causal_conv1d_update_prefill, one thread per channel walking the tokens.