sm_120 RTX 5080 CUDA kernel crash with hunyuan.py - "no kernel image is available"

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## Summary

When running FramePack on an **RTX 5080** (Blackwell architecture, CUDA capability `sm_120`), the pipeline crashes with:

RuntimeError: CUDA error: no kernel image is available for execution on the device

This happens inside `hunyuan.py`, specifically on this line:

```python
llama_attention_length = int(llama_attention_mask.sum())
```

Additionally, PyTorch emits the following warning:

UserWarning: NVIDIA GeForce RTX 5080 with CUDA capability sm_120 is not compatible with the current PyTorch installation.

## Environment

- GPU: NVIDIA GeForce RTX 5080
- Driver: Studio 577.00 (latest)
- CUDA Version: 12.6+
- Torch Version: 2.6.0+cu126
- Operating System: Windows 11
- FramePack Version: framepack_cu126_torch26 one-click package

## Output of `torch.cuda.get_device_capability(0)`

(12, 0)

Start with hunyuan.py at the llama_attention_mask.sum() call and reproduce the failure on an RTX 5080 using the reported FramePack package, PyTorch 2.6.0+cu126, and Windows 11 environment. Check the reported sm_120 compatibility warning and verify that the pipeline completes without the CUDA kernel-image crash when done.

Written by the indexing model from the issue text.