feat(cccl): integrate missing CCCL directories — python/, ci/, .agent/, docs/, test/

Sparse-checkout from NVIDIA/cccl main branch to complete cccl_upstream:

Added:
- python/cuda_cccl/ (226 files) — Python bindings for device-level algorithms
  Critical for muh toolchain: cuda.compute.reduce_into, scan, radix_sort, etc.
  Includes 204 .py files with full test coverage for all 27 algorithms
- ci/ (163 files) — Build/test infrastructure
  build_cub.sh, test_cub.sh, build_and_test_targets.sh, matrix.yaml
  Directly maps to our [INFRA-CI] and [INFRA-BUILD] items
- .agent/skills/ (7 files) — NVIDIA's own agent skills for CCCL
  cccl-style/SKILL.md, cccl-test/SKILL.md, sass-diff/SKILL.md
- docs/ (491 files) — Official CCCL documentation
  CI references, CMake guides, Python compute docs, libcudacxx PTX docs
- test/ (12 files) — Top-level integration tests (cuda_smoke, stdpar)
- Root configs: .clang-format, .clang-tidy, CONTRIBUTING.md, pyproject.toml
- CLAUDE.md symlink → AGENTS.md (NVIDIA's standard)

cccl_upstream now mirrors full NVIDIA/cccl structure:
  Before: 42M (cub + thrust + libcudacxx + cudax + c + examples + benchmarks)
  After:  53M (+python +ci +docs +.agent +test +configs)

This completes the CCCL base needed for:
- [muh-bench] items: ci/util/build_and_test_targets.sh for targeted builds
- [CCCL-verify] items: python/cuda_cccl/tests/ as reference implementations
- [CCCL-test] items: ci/test_cub.sh, ci/test_thrust.sh
- Agent workflow: .agent/skills/ for consistent style and test patterns

cccl_upstream/ci/compile_time/prepare_traces.py

@@ -0,0 +1,167 @@
+#!/usr/bin/env python3
+
+import argparse
+import json
+from pathlib import Path
+
+DETAIL_EVENT_NAMES = {
+    "Code Generation Function",
+    "CodeGen Function",
+    "ExecuteCompiler",
+    "Frontend",
+    "Instantiating Template Class",
+    "Instantiating Template Function",
+    "InstantiateClass",
+    "InstantiateFunction",
+    "OptFunction",
+    "ParseClass",
+    "PerformPendingInstantiations",
+    "Processing Header File",
+    "RunPass",
+    "Scanning Function Body",
+    "Source",
+}
+
+DETAIL_PREFIXES_TO_STRIP = (
+    "libcudacxx/include/",
+    "cudax/include/",
+    "c/parallel/include/",
+)
+
+DETAIL_PREFIXES_TO_COLLAPSE = (
+    ("cub/cub/", "cub/"),
+    ("thrust/thrust/", "thrust/"),
+)
+
+
+def normalize_detail(detail: str, repo_root: Path) -> str:
+    detail_path = Path(detail)
+    if detail_path.is_absolute():
+        try:
+            rel = detail_path.resolve(strict=False).relative_to(repo_root)
+            detail = rel.as_posix()
+        except ValueError:
+            pass
+
+    for prefix in DETAIL_PREFIXES_TO_STRIP:
+        if detail.startswith(prefix):
+            detail = detail[len(prefix) :]
+            break
+
+    for prefix, replacement in DETAIL_PREFIXES_TO_COLLAPSE:
+        if detail.startswith(prefix):
+            detail = replacement + detail[len(prefix) :]
+            break
+
+    return detail
+
+
+def display_detail(detail: str, repo_root: Path, max_detail_len: int | None) -> str:
+    detail = normalize_detail(detail, repo_root)
+    if (
+        max_detail_len is not None
+        and max_detail_len > 0
+        and len(detail) > max_detail_len
+    ):
+        return detail[: max_detail_len - 1] + "..."
+    return detail
+
+
+def rewrite_event_name(
+    event: dict, repo_root: Path, max_detail_len: int | None
+) -> bool:
+    name = event.get("name")
+    if name not in DETAIL_EVENT_NAMES:
+        return False
+
+    args = event.get("args")
+    if not isinstance(args, dict):
+        return False
+
+    detail = args.get("detail")
+    if not detail:
+        return False
+
+    args.setdefault("original_name", name)
+    event["name"] = f"{name}: {display_detail(str(detail), repo_root, max_detail_len)}"
+    return True
+
+
+def prepare_trace(
+    input_path: Path, output_path: Path, repo_root: Path, max_detail_len: int | None
+) -> int:
+    with input_path.open(encoding="utf-8") as f:
+        trace = json.load(f)
+
+    rewritten = 0
+    for event in trace.get("traceEvents", []):
+        if rewrite_event_name(event, repo_root, max_detail_len):
+            rewritten += 1
+
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    with output_path.open("w", encoding="utf-8") as f:
+        json.dump(trace, f, separators=(",", ":"))
+
+    return rewritten
+
+
+def iter_input_traces(input_path: Path) -> list[Path]:
+    if input_path.is_file():
+        return [input_path]
+    return sorted(input_path.rglob("*.json"))
+
+
+def output_path_for(input_trace: Path, input_root: Path, output_path: Path) -> Path:
+    if input_root.is_file():
+        if output_path.is_dir() or not output_path.suffix:
+            return output_path / f"{input_trace.stem}.perfetto.json"
+        return output_path
+
+    rel = input_trace.relative_to(input_root)
+    return output_path / rel.parent / f"{rel.stem}.perfetto.json"
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Prepare NVCC device-time-trace JSON files for Perfetto by promoting args.detail into event names."
+    )
+    parser.add_argument(
+        "--input", required=True, type=Path, help="Input trace JSON file or directory"
+    )
+    parser.add_argument(
+        "--output", required=True, type=Path, help="Output trace JSON file or directory"
+    )
+    parser.add_argument(
+        "--repo-root", default=Path(__file__).resolve().parents[2], type=Path
+    )
+    parser.add_argument(
+        "--max-detail-len",
+        default=0,
+        type=int,
+        help="Truncate promoted detail text to this many characters; 0 keeps full details",
+    )
+    args = parser.parse_args()
+
+    input_path = args.input.resolve(strict=False)
+    output_path = args.output.resolve(strict=False)
+    repo_root = args.repo_root.resolve(strict=False)
+    max_detail_len = args.max_detail_len if args.max_detail_len > 0 else None
+
+    traces = iter_input_traces(input_path)
+    if not traces:
+        raise SystemExit(f"no JSON traces found under {args.input}")
+
+    total_rewritten = 0
+    for trace_path in traces:
+        total_rewritten += prepare_trace(
+            trace_path,
+            output_path_for(trace_path, input_path, output_path),
+            repo_root,
+            max_detail_len,
+        )
+
+    print(f"prepared {len(traces)} trace(s); renamed {total_rewritten} event(s)")
+
+
+if __name__ == "__main__":
+    main()