Function reshape_and_cache 

pub fn reshape_and_cache(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    key: DevicePtr,
    value: DevicePtr,
    k_cache: DevicePtr,
    v_cache: DevicePtr,
    slot_mapping: DevicePtr,
    num_tokens: u32,
    num_kv_heads: u32,
    head_dim: u32,
    block_size: u32,
    key_stride: u32,
    value_stride: u32,
    _cache_stride: u64,
    stream: u64,
) -> Result<()>

Write K/V to paged FP8 cache using slot_mapping.

Kernel: reshape_and_cache_flash_fp8(key, value, k_cache, v_cache, slot_mapping, num_kv_heads, head_dim, block_size, k_scale, v_scale, key_stride, value_stride, cache_stride) Grid: (num_tokens, 1, 1) Block: (256, 1, 1)

slot_mapping is a device pointer to i64[num_tokens]. BF16 reshape and cache — no quantization, direct BF16 copy.