Function gdn_decode_chunk3 

pub fn gdn_decode_chunk3(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    h_state: DevicePtr,
    query: DevicePtr,
    key: DevicePtr,
    value: DevicePtr,
    gate: DevicePtr,
    beta: DevicePtr,
    output: DevicePtr,
    h_state_inter0: DevicePtr,
    h_state_inter1: DevicePtr,
    batch_size: u32,
    num_k_heads: u32,
    num_v_heads: u32,
    k_dim: u32,
    v_dim: u32,
    qk_stride: u32,
    v_stride: u32,
    gb_stride: u32,
    stream: u64,
) -> Result<()>

Fused 3-token GDN decode (K=3 speculative verification).

Processes exactly 3 tokens through GDN in a single kernel launch. Saves 2 intermediate H states (H_1, H_2) for rollback on draft rejection. 4 passes vs 6 for 3× sequential decode.

Kernel: gated_delta_rule_chunk3(h_state, query, key, value, gate, beta, output, h_inter0, h_inter1, batch_size, num_k_heads, num_v_heads, k_dim, v_dim, qk_stride, v_stride, gb_stride) Grid: (num_v_heads, batch, 1) Block: (128, 1, 1)