[CCCL] Add missing CCCL components: c2h, nvbench_helper, cmake, cudax, AGENTS.md

Added 863 files from NVIDIA/cccl sparse checkout:
- c2h/ (27 files): Catch2 test helpers — generators, validators, runner
- nvbench_helper/ (10 files): Benchmark harness utilities
- cmake/ (29 files): CMake presets and build helpers
- cudax/ (794 files): Experimental CUDA extensions
- AGENTS.md: NVIDIA's official AI agent instructions for CCCL
- CMakePresets.json: Standardized build configurations
- cccl-version.json: Version tracking

Also added CCCL_ASSET_MAP.md mapping all 4295 CCCL files to
competition value and PRD items.

cccl_upstream now covers 100% of competition-critical assets:
- 27 tuning headers (SM80/90/100 benchmark data)
- 32 dispatch headers (algorithm implementations)
- 60 Thrust examples (correctness verification)
- 217 CUB Catch2 tests (regression matrix)
- 153 CUB benchmarks (parameter space search)
- 18 CUB examples (API verification)
- 27 test helpers + benchmark harness
- 794 cudax experimental extensions

cccl_upstream/cmake/CCCLConfigureTarget.cmake

@@ -0,0 +1,66 @@
+set(CCCL_EXECUTABLE_OUTPUT_DIR "${CCCL_BINARY_DIR}/bin")
+set(CCCL_LIBRARY_OUTPUT_DIR "${CCCL_BINARY_DIR}/lib")
+
+# Setup common properties for all test/example/etc targets.
+function(cccl_configure_target target_name)
+  set(options)
+  set(oneValueArgs DIALECT)
+  set(multiValueArgs)
+  cmake_parse_arguments(
+    CCT
+    "${options}"
+    "${oneValueArgs}"
+    "${multiValueArgs}"
+    ${ARGN}
+  )
+
+  get_target_property(type ${target_name} TYPE)
+
+  set_target_properties(
+    ${target_name}
+    PROPERTIES
+      # Disable compiler extensions:
+      CXX_EXTENSIONS OFF
+      CUDA_EXTENSIONS OFF
+  )
+
+  if (DEFINED CCT_DIALECT)
+    set(CMAKE_CXX_STANDARD ${CCT_DIALECT})
+    set(CMAKE_CUDA_STANDARD ${CCT_DIALECT})
+  endif()
+
+  set_target_properties(
+    ${target_name}
+    PROPERTIES
+      CXX_STANDARD ${CMAKE_CXX_STANDARD}
+      CUDA_STANDARD ${CMAKE_CUDA_STANDARD}
+      CXX_STANDARD_REQUIRED ON
+      CUDA_STANDARD_REQUIRED ON
+  )
+
+  get_property(langs GLOBAL PROPERTY ENABLED_LANGUAGES)
+  set(dialect_features)
+  if (CUDA IN_LIST langs)
+    list(APPEND dialect_features cuda_std_${CMAKE_CUDA_STANDARD})
+  endif()
+  if (CXX IN_LIST langs)
+    list(APPEND dialect_features cxx_std_${CMAKE_CXX_STANDARD})
+  endif()
+
+  get_target_property(type ${target_name} TYPE)
+  if (${type} STREQUAL "INTERFACE_LIBRARY")
+    target_compile_features(${target_name} INTERFACE ${dialect_features})
+  else()
+    target_compile_features(${target_name} PUBLIC ${dialect_features})
+  endif()
+
+  if (NOT ${type} STREQUAL "INTERFACE_LIBRARY")
+    set_target_properties(
+      ${target_name}
+      PROPERTIES
+        ARCHIVE_OUTPUT_DIRECTORY "${CCCL_LIBRARY_OUTPUT_DIR}"
+        LIBRARY_OUTPUT_DIRECTORY "${CCCL_LIBRARY_OUTPUT_DIR}"
+        RUNTIME_OUTPUT_DIRECTORY "${CCCL_EXECUTABLE_OUTPUT_DIR}"
+    )
+  endif()
+endfunction()