ref(upstream): FULL TREE — Deep-Spark xllm (1470) + ds_vllm csrc/models (703)

Replaces cherry-picked upstream_ref with complete source trees.

xllm/ — Iluvatar official C++ inference engine (15MB, 1470 files)
  Complete: kernels → layers → models → runtime → scheduler → api
  Excluded: .git, binary images, third_party submodule checkouts

ds_vllm/ — Iluvatar official vllm fork (8MB, 703 files)
  Included: csrc/ (ALL CUDA kernels), fused_moe/, qwen3_5 model, _custom_ops
  Excluded: tests, benchmarks, docs, examples (not needed for reference)

Critical call chains now fully traceable:
  MoE: moe_topk_softmax_kernels.cuh → ixformer.h → fused_moe.cpp → layer
  GDN: qwen3_gated_delta_net_base.cpp → qwen3_5_gated_delta_net.cpp
  Attention: ixformer.h → xllm_paged_attention → attention.cpp

upstream_ref/xllm/docs/en/features/ppmatmul.md

@@ -0,0 +1,36 @@
+# PpMatmul Operator Optimization
+
+## Background
+
+In the inference of large models, matrix multiplication accounts for a high proportion and takes a long time. We have optimized the implementation of the matrix multiplication operator.
+
+## Feature Introduction
+
+The PpMatmul operator uses a Tiling strategy to decompose matrix multiplication into multiple smaller matrix multiplication tasks. However, when the number of tiles is small, tasks cannot be evenly distributed across all NPU cores, leading to the tail effect problem, which affects computational efficiency. We optimize the performance of the PpMatmul operator by prefetching memory or redistributing tasks.
+
+## User Interface
+
+### Operator Direct Call API
+
+```cpp
+aclnnStatus aclnnPpMatmulOptGetWorkspaceSize(
+    const aclTensor *a,
+    const aclTensor *b,
+    const aclTensor *out,
+    uint64_t *workspaceSize,
+    aclOpExecutor **executor);
+
+aclnnStatus aclnnPpMatmulOpt(
+    void *workspace,
+    uint64_t workspaceSize,
+    aclOpExecutor *executor,
+    aclrtStream stream);
+```
+
+- `a`: Input matrix A.
+- `b`: Input matrix B.
+- `out`: Output matrix, storing the computation result.
+
+## Performance Effect
+
+For cases with a small number of tiles (e.g., when M is small, corresponding to a small batch size), there is an **18%** performance improvement of the operator compared to before optimization when (TP=4).