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/FindRust.cmake

@@ -0,0 +1,73 @@
+# ported from https://github.com/Devolutions/CMakeRust
+set(_CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ${CMAKE_FIND_ROOT_PATH_MODE_PROGRAM})
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM BOTH)
+set(_CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ${CMAKE_FIND_ROOT_PATH_MODE_INCLUDE})
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE BOTH)
+
+if(CMAKE_HOST_WIN32)
+	set(USER_HOME "$ENV{USERPROFILE}")
+else()
+	set(USER_HOME "$ENV{HOME}")
+endif()
+
+if(NOT DEFINED CARGO_HOME)
+	if("$ENV{CARGO_HOME}" STREQUAL "")
+		set(CARGO_HOME "${USER_HOME}/.cargo")
+	else()
+		set(CARGO_HOME "$ENV{CARGO_HOME}")
+	endif()
+endif()
+
+# Find cargo executable
+find_program(CARGO_EXECUTABLE cargo
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(CARGO_EXECUTABLE)
+
+# Find rustc executable
+find_program(RUSTC_EXECUTABLE rustc
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(RUSTC_EXECUTABLE)
+
+# Find rustdoc executable
+find_program(RUSTDOC_EXECUTABLE rustdoc
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(RUSTDOC_EXECUTABLE)
+
+# Find rust-gdb executable
+find_program(RUST_GDB_EXECUTABLE rust-gdb
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(RUST_GDB_EXECUTABLE)
+
+# Find rust-lldb executable
+find_program(RUST_LLDB_EXECUTABLE rust-lldb
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(RUST_LLDB_EXECUTABLE)
+
+# Find rustup executable
+find_program(RUSTUP_EXECUTABLE rustup
+	HINTS "${CARGO_HOME}"
+	PATH_SUFFIXES "bin")
+mark_as_advanced(RUSTUP_EXECUTABLE)
+
+set(RUST_FOUND FALSE CACHE INTERNAL "")
+
+if(CARGO_EXECUTABLE AND RUSTC_EXECUTABLE AND RUSTDOC_EXECUTABLE)
+	set(RUST_FOUND TRUE CACHE INTERNAL "")
+
+	set(CARGO_HOME "${CARGO_HOME}" CACHE PATH "Rust Cargo Home")
+
+	execute_process(COMMAND ${RUSTC_EXECUTABLE} --version OUTPUT_VARIABLE RUSTC_VERSION OUTPUT_STRIP_TRAILING_WHITESPACE)
+	string(REGEX REPLACE "rustc ([^ ]+) .*" "\\1" RUSTC_VERSION "${RUSTC_VERSION}")
+endif()
+
+if(NOT RUST_FOUND)
+	message(FATAL_ERROR "Could not find Rust!")
+endif()
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM ${_CMAKE_FIND_ROOT_PATH_MODE_PROGRAM})
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ${_CMAKE_FIND_ROOT_PATH_MODE_INCLUDE})