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/cmake/cc_binary.cmake

@@ -0,0 +1,60 @@
+include(CMakeParseArguments)
+
+# inspired by https://github.com/abseil/abseil-cpp
+# cc_binary()
+# CMake function to imitate Bazel's cc_binary rule.
+#
+# Parameters:
+# NAME: name of target
+# HDRS: List of public header files for the library
+# SRCS: List of source files for the library
+# COPTS: List of private compile options
+# DEFINES: List of public defines
+# LINKOPTS: List of link options
+# DEPS: List of other libraries to be linked in to the binary targets
+#
+# cc_library(
+#   NAME
+#     awesome
+#   HDRS
+#     "a.h"
+#   SRCS
+#     "a.cc"
+# )
+# cc_binary(
+#   NAME
+#     fantastic
+#   SRCS
+#     "b.cc"
+#   DEPS
+#     :awesome
+# )
+#
+function(cc_binary)
+  cmake_parse_arguments(
+    CC_BINARY # prefix
+    "" # options
+    "NAME" # one value args
+    "HDRS;SRCS;COPTS;DEFINES;LINKOPTS;DEPS" # multi value args
+    ${ARGN}
+  )
+
+  add_executable(${CC_BINARY_NAME} "")
+  target_sources(${CC_BINARY_NAME} 
+    PRIVATE ${CC_BINARY_SRCS} ${CC_BINARY_HDRS}
+  )
+  target_link_libraries(${CC_BINARY_NAME}
+    PUBLIC 
+      ${CC_BINARY_DEPS}
+    PRIVATE
+      ${CC_BINARY_LINKOPTS}
+  )
+  target_include_directories(${CC_BINARY_NAME}
+    PUBLIC
+      "$<BUILD_INTERFACE:${COMMON_INCLUDE_DIRS}>"      
+  )
+  target_compile_options(${CC_BINARY_NAME} PRIVATE ${CC_BINARY_COPTS})
+  target_compile_definitions(${CC_BINARY_NAME} PUBLIC ${CC_BINARY_DEFINES})
+
+  add_executable(:${CC_BINARY_NAME} ALIAS ${CC_BINARY_NAME})
+endfunction()