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/third_party/CMakeLists.txt

@@ -0,0 +1,66 @@
+include(cc_library)
+
+add_subdirectory(sentencepiece)
+add_subdirectory(minja)
+add_subdirectory(brpc)
+add_subdirectory(smhasher/src)
+add_subdirectory(cpprestsdk)
+set(CPPREST_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/cpprestsdk/Release/include)
+set(CPPREST_LIB ${CMAKE_BINARY_DIR}/third_party/cpprestsdk/Release/Binaries/libcpprest.a)
+
+# GCC 12+ strict check workaround for cpprestsdk
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND 
+   CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 12)
+    if(TARGET cpprest)
+        target_compile_options(cpprest PRIVATE -Wno-restrict -Wno-attributes)
+        message(STATUS "Applied GCC 12+ warning suppressions for cpprestsdk")
+    endif()
+endif()
+
+add_subdirectory(etcd_cpp_apiv3)
+add_subdirectory(xxHash)
+add_subdirectory(spdlog)
+
+if(USE_NPU)
+  add_subdirectory(torch_npu_ops)
+endif()
+add_subdirectory(Mooncake)
+
+target_include_directories(mooncake_store PUBLIC
+  ${CMAKE_CURRENT_SOURCE_DIR}/Mooncake/mooncake-transfer-engine/include
+)
+
+if(USE_ILU)
+  if(TARGET cpprest)
+      set_target_properties(cpprest PROPERTIES
+          CXX_STANDARD 20
+          CXX_STANDARD_REQUIRED ON
+          CXX_EXTENSIONS OFF
+      )
+  endif()
+  if(TARGET transfer_engine)
+    target_compile_options(transfer_engine PRIVATE -std=c++20)
+    set_target_properties(transfer_engine PROPERTIES
+        CXX_STANDARD 20
+        CXX_STANDARD_REQUIRED ON
+    )
+    message(STATUS "Set C++20 for transfer_engine target")
+  endif()
+  if(TARGET SMHasherSupport)
+      set_target_properties(SMHasherSupport PROPERTIES
+          CXX_STANDARD 11
+          CXX_STANDARD_REQUIRED ON
+          CXX_EXTENSIONS OFF
+      )
+      message(STATUS "SMHasherSupport target found and configured")
+  else()
+      message(WARNING "SMHasherSupport target not found after adding smhasher")
+  endif()
+endif()
+
+## The order of static libraries is important in the CMake build system because the linker processes them strictly from left to right. 
+## -> The linker scans each library only once and extracts object files solely to resolve currently undefined symbols.
+## -> In modern CMake, the best practice is to explicitly declare a target's dependencies, allowing CMake to automatically determine the correct linking order. 
+## -> The following code is added to prevent symbol resolution errors when xllm links against mooncake-related static libraries.
+target_link_libraries(mooncake_store PUBLIC transfer_engine cachelib_memory_allocator)
+target_link_libraries(cachelib_memory_allocator PRIVATE Folly::folly glog::glog)