feat(CRITICAL): 从 GitHub 扫描搬运 ixformer SDK + xllm 完整 GDN/MoE 代码

来源:
  1. Chranos/ixformer (GitHub) → ixformer_sdk/ (230 files, 70K lines)
     - inference/functions/vllm.py: vllm_moe_topk_softmax 完整实现 (2033 lines)
     - inference/functions/moe.py: MoE ops 完整实现 (1380 lines)
     - contrib/vllm_flash_attn/: FA2 Python 接口 (1018 lines)
     - contrib/tgi/fused_moe.py: TGI fused MoE (429 lines)
     - csrc/include/ixformer/: C++ kernel headers + cmake

  2. Deep-Spark/xllm (GitHub) → upstream_ref/xllm_latest/ (+15 files)
     - npu_torch/qwen3_5_decoder_layer_impl.cpp/.h
     - npu_torch/qwen3_5_gated_delta_net.cpp/.h
     - npu_torch/qwen3_next_*.cpp/.h (6 files)
     - npu_torch/attention.cpp/.h + fused_moe.cpp/.h + CMakeLists.txt
     - models/llm/qwen3_5.h + qwen3_5_mtp.h + qwen3_next.h
     - models/vlm/qwen3_5.h

调用链完整性:
  ixformer_sdk/inference/functions/vllm.py
    → ops.infer.moe_topk_softmax() (C++ 层)
    → 这就是 base 镜像 libixformer.so 里的实现

  upstream_ref/xllm_latest/core/layers/ilu/fused_moe.cpp
    → ixformer::infer::topk_softmax() (直接 C++ 调用)
    → ixformer::infer::group_gemm() → 完整 7-step MoE pipeline

ixformer_sdk/contrib/flashinfer/activation.py

@@ -0,0 +1,29 @@
+import ixformer.inference.functions as ops
+import torch
+
+
+def gelu_and_mul():
+    pass
+
+
+def gelu_tanh_and_mul():
+    pass
+
+
+def silu_and_mul(input: torch.Tensor, out: torch.Tensor = None) -> torch.Tensor:
+    r"""Fused SiLU and Mul operation.
+
+    Parameters
+    ----------
+    input: torch.Tensor
+        Input tensor, shape (..., 2 * hidden_size).
+
+    out: Optional[torch.Tensor]
+        The the output tensor, if specified, the kernel will update this tensor inplace.
+
+    Returns
+    -------
+    output: torch.Tensor
+        Output tensor, shape (..., hidden_size).
+    """
+    return ops.silu_and_mul(input=input, output=out)