[INFRA] Import NVIDIA/CCCL upstream as optimization reference library

CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0

cccl_upstream/c/parallel.v2/test/freestanding/test_util.h

@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of CUDA Experimental in CUDA C++ Core Libraries,
+// under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef C_PARALLEL_FREESTANDING_TEST_UTIL_H
+#define C_PARALLEL_FREESTANDING_TEST_UTIL_H
+
+#include <cassert>
+#include <iostream>
+
+#include <cuda_runtime.h>
+
+#define CUDA_CHECK(call)                                                                                       \
+  do                                                                                                           \
+  {                                                                                                            \
+    cudaError_t err = call;                                                                                    \
+    if (err != cudaSuccess)                                                                                    \
+    {                                                                                                          \
+      std::cerr << "CUDA error at " << __FILE__ << ":" << __LINE__ << ": " << cudaGetErrorString(err) << "\n"; \
+      return 1;                                                                                                \
+    }                                                                                                          \
+  } while (0)
+
+#endif // C_PARALLEL_FREESTANDING_TEST_UTIL_H