Extracted torch_chunk_gated_delta_rule and torch_recurrent_gated_delta_rule
from xllm_latest/core/layers/npu_torch/qwen3_gated_delta_net_base.cpp.
Pure PyTorch C++ — no NPU/ACL deps, no custom CUDA kernels.
Same algorithm as our Python _torch_chunk_gated_delta_rule but
avoids Python interpreter overhead in the chunk loop.
Verify on real BI-V100: python3 verify_gdn_cpp.py
