Function qsa_block_pool 

pub fn qsa_block_pool(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    raw_keys: DevicePtr,
    k_norm_w: DevicePtr,
    block_keys: DevicePtr,
    first_block: u32,
    n_new: u32,
    ratio: u32,
    hd: u32,
    rot: u32,
    theta: f32,
    eps: f32,
    stream: u64,
) -> Result<()>

Pool n_new freshly complete blocks starting at first_block: mean over ratio raw keys -> RMSNorm*(1+w) -> rope at block-start pos.