[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/c2h/generators_gen_values.cu

@@ -0,0 +1,96 @@
+// SPDX-FileCopyrightText: Copyright (c) 2011-2025, NVIDIA CORPORATION. All rights reserved.
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include <thrust/tabulate.h>
+#include <thrust/transform.h>
+
+#include <c2h/bfloat16.cuh>
+#include <c2h/detail/generators.cuh>
+#include <c2h/device_policy.h>
+#include <c2h/extended_types.h>
+#include <c2h/generators.h>
+#include <c2h/half.cuh>
+
+namespace c2h::detail
+{
+template <typename T>
+void gen_values_between(seed_t seed, ::cuda::std::span<T> data, T min, T max)
+{
+  const auto* dist = prepare_random_data(seed, data.size());
+  thrust::transform(device_policy, dist, dist + data.size(), data.begin(), random_to_item_t<T>(min, max));
+}
+
+template <typename T>
+struct counter_to_cyclic_item_t
+{
+  std::size_t n;
+
+  template <typename CounterT>
+  __device__ T operator()(CounterT id)
+  {
+    // This has to be a type for which extended floating point types like __nv_fp8_e5m2 provide an overload
+    return static_cast<T>(static_cast<float>(static_cast<uint64_t>(id) % n));
+  }
+};
+
+template <typename T>
+void gen_values_cyclic(modulo_t mod, ::cuda::std::span<T> data)
+{
+  thrust::tabulate(device_policy, data.begin(), data.end(), counter_to_cyclic_item_t<T>{mod.get()});
+}
+
+#define INSTANTIATE_RND(TYPE) \
+  template void gen_values_between<TYPE>(seed_t, ::cuda::std::span<TYPE> data, TYPE min, TYPE max)
+#define INSTANTIATE_MOD(TYPE) template void gen_values_cyclic<TYPE>(modulo_t, ::cuda::std::span<TYPE> data)
+
+#define INSTANTIATE(TYPE) \
+  INSTANTIATE_RND(TYPE);  \
+  INSTANTIATE_MOD(TYPE)
+
+INSTANTIATE(std::uint8_t);
+INSTANTIATE(std::uint16_t);
+INSTANTIATE(std::uint32_t);
+INSTANTIATE(std::uint64_t);
+
+INSTANTIATE(std::int8_t);
+INSTANTIATE(std::int16_t);
+INSTANTIATE(std::int32_t);
+INSTANTIATE(std::int64_t);
+
+#if _CCCL_HAS_NVFP8()
+INSTANTIATE(__nv_fp8_e5m2);
+INSTANTIATE(__nv_fp8_e4m3);
+#endif // _CCCL_HAS_NVFP8()
+INSTANTIATE(float);
+INSTANTIATE(double);
+INSTANTIATE(cuda::std::complex<float>);
+INSTANTIATE(cuda::std::complex<double>);
+
+INSTANTIATE(bool);
+INSTANTIATE(char);
+
+#if TEST_HALF_T()
+INSTANTIATE(half_t);
+INSTANTIATE(__half);
+#  if _CCCL_CTK_AT_LEAST(12, 2)
+INSTANTIATE(cuda::std::complex<__half>);
+#  endif // _CCCL_CTK_AT_LEAST(12, 2)
+#endif // TEST_HALF_T()
+
+#if TEST_BF_T()
+INSTANTIATE(bfloat16_t);
+INSTANTIATE(__nv_bfloat16);
+#  if _CCCL_CTK_AT_LEAST(12, 2)
+INSTANTIATE(cuda::std::complex<__nv_bfloat16>);
+#  endif // _CCCL_CTK_AT_LEAST(12, 2)
+#endif // TEST_BF_T()
+
+#if TEST_INT128()
+INSTANTIATE(__int128_t);
+INSTANTIATE(__uint128_t);
+#endif // TEST_INT128()
+
+#undef INSTANTIATE_RND
+#undef INSTANTIATE_MOD
+#undef INSTANTIATE
+} // namespace c2h::detail