[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/libcudacxx/include/cuda/__functional/minimum.h

@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of libcu++, the C++ Standard Library for your entire system,
+// 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) 2025 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _CUDA_FUNCTIONAL_MINIMUM_H
+#define _CUDA_FUNCTIONAL_MINIMUM_H
+
+#include <cuda/std/detail/__config>
+
+#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
+#  pragma GCC system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
+#  pragma clang system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
+#  pragma system_header
+#endif // no system header
+
+#include <cuda/__functional/minimum_maximum_common.h>
+#include <cuda/std/__cmath/min_max.h>
+#include <cuda/std/__type_traits/common_type.h>
+#include <cuda/std/__type_traits/is_extended_floating_point.h>
+#include <cuda/std/__type_traits/is_floating_point.h>
+#include <cuda/std/__utility/ctad_support.h>
+
+#include <cuda/std/__cccl/prologue.h>
+
+_CCCL_BEGIN_NAMESPACE_CUDA
+
+template <class _Tp = void>
+struct _CCCL_TYPE_VISIBILITY_DEFAULT minimum
+{
+  _CCCL_EXEC_CHECK_DISABLE
+  [[nodiscard]] _CCCL_API constexpr _Tp operator()(const _Tp& __lhs, const _Tp& __rhs) const
+    noexcept(__is_maximum_minimum_noexcept_v<_Tp, _Tp, _Tp>)
+  {
+    if constexpr (::cuda::std::is_floating_point_v<_Tp> || ::cuda::std::__is_extended_floating_point_v<_Tp>)
+    {
+      return ::cuda::std::fmin(__lhs, __rhs);
+    }
+    else
+    {
+      return (__lhs < __rhs) ? __lhs : __rhs;
+    }
+  }
+};
+_CCCL_CTAD_SUPPORTED_FOR_TYPE(minimum);
+
+template <>
+struct _CCCL_TYPE_VISIBILITY_DEFAULT minimum<void>
+{
+  _CCCL_EXEC_CHECK_DISABLE
+  template <class _Tp, class _Up, class _Common = ::cuda::std::common_type_t<_Tp, _Up>>
+  [[nodiscard]] _CCCL_API constexpr _Common operator()(const _Tp& __lhs, const _Up& __rhs) const
+    noexcept(__is_maximum_minimum_noexcept_v<_Tp, _Up, _Common>)
+  {
+    if constexpr (::cuda::std::is_floating_point_v<_Common> || ::cuda::std::__is_extended_floating_point_v<_Common>)
+    {
+      return ::cuda::std::fmin(static_cast<_Common>(__lhs), static_cast<_Common>(__rhs));
+    }
+    else
+    {
+      return (__lhs < __rhs) ? __lhs : __rhs;
+    }
+  }
+};
+
+_CCCL_END_NAMESPACE_CUDA
+
+#include <cuda/std/__cccl/epilogue.h>
+
+#endif // _CUDA_FUNCTIONAL_MINIMUM_H