Function ssm_h_state_f32_to_f16 

pub fn ssm_h_state_f32_to_f16(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    src: DevicePtr,
    dst: DevicePtr,
    n: u64,
    stream: u64,
) -> Result<()>

2026-09-25: FP32 -> FP16 conversion of n h-state elements (ssm_h_state_f32_to_f16, round-to-nearest-even). The kernel is grid-stride, so the clamped grid still covers every element. src and dst must not alias: an in-place narrowing conversion is a data race.