[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/cudax/test/utility/scope.cu

@@ -0,0 +1,191 @@
+//===----------------------------------------------------------------------===//
+//
+// 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) 2025 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#include <cuda/experimental/__utility/scope.cuh>
+
+#include <utility>
+
+#include <c2h/catch2_test_helper.h>
+
+namespace cudax = cuda::experimental;
+
+TEST_CASE("scope_exit runs on normal exit", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_exit guard{[&]() noexcept {
+      ++count;
+    }};
+    CHECK(count == 0);
+  }
+  CHECK(count == 1);
+}
+
+TEST_CASE("scope_exit runs on exceptional exit", "[utility][scope]")
+{
+  int count   = 0;
+  bool caught = false;
+  try
+  {
+    cudax::scope_exit guard{[&]() noexcept {
+      ++count;
+    }};
+    throw 42;
+  }
+  catch (...)
+  {
+    caught = true;
+  }
+  CHECK(caught);
+  CHECK(count == 1);
+}
+
+TEST_CASE("scope_exit release disables the guard", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_exit guard{[&]() noexcept {
+      ++count;
+    }};
+    guard.release();
+  }
+  CHECK(count == 0);
+}
+
+TEST_CASE("scope_exit move releases the source", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_exit first{[&]() noexcept {
+      ++count;
+    }};
+    auto second = std::move(first);
+    CHECK(count == 0);
+  }
+  CHECK(count == 1);
+}
+
+TEST_CASE("scope_fail runs only on exceptional exit", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_fail guard{[&]() noexcept {
+      ++count;
+    }};
+  }
+  CHECK(count == 0);
+
+  bool caught = false;
+  try
+  {
+    cudax::scope_fail guard{[&]() noexcept {
+      ++count;
+    }};
+    throw 42;
+  }
+  catch (...)
+  {
+    caught = true;
+  }
+  CHECK(caught);
+  CHECK(count == 1);
+}
+
+TEST_CASE("scope_fail release disables the guard", "[utility][scope]")
+{
+  int count   = 0;
+  bool caught = false;
+  try
+  {
+    cudax::scope_fail guard{[&]() noexcept {
+      ++count;
+    }};
+    guard.release();
+    throw 42;
+  }
+  catch (...)
+  {
+    caught = true;
+  }
+  CHECK(caught);
+  CHECK(count == 0);
+}
+
+TEST_CASE("scope_fail move releases the source", "[utility][scope]")
+{
+  int count   = 0;
+  bool caught = false;
+  try
+  {
+    cudax::scope_fail first{[&]() noexcept {
+      ++count;
+    }};
+    auto second = std::move(first);
+    throw 42;
+  }
+  catch (...)
+  {
+    caught = true;
+  }
+  CHECK(caught);
+  CHECK(count == 1);
+}
+
+TEST_CASE("scope_success runs only on normal exit", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_success guard{[&] {
+      ++count;
+    }};
+  }
+  CHECK(count == 1);
+
+  count       = 0;
+  bool caught = false;
+  try
+  {
+    cudax::scope_success guard{[&] {
+      ++count;
+    }};
+    throw 42;
+  }
+  catch (...)
+  {
+    caught = true;
+  }
+  CHECK(caught);
+  CHECK(count == 0);
+}
+
+TEST_CASE("scope_success release disables the guard", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_success guard{[&] {
+      ++count;
+    }};
+    guard.release();
+  }
+  CHECK(count == 0);
+}
+
+TEST_CASE("scope_success move releases the source", "[utility][scope]")
+{
+  int count = 0;
+  {
+    cudax::scope_success first{[&] {
+      ++count;
+    }};
+    auto second = std::move(first);
+    CHECK(count == 0);
+  }
+  CHECK(count == 1);
+}