Include cuda.core C++ .h files in packages

[fallintoplace]

Summary

• Include _cpp/*.h in the cuda-core source distribution manifest.
• Include _cpp/*.h in setuptools package data so wheel builds carry the C++ helper header.

Why

cuda/core/_tensor_map.pyx includes _cpp/tensor_map_cccl.h, but the _cpp packaging metadata only included .hpp headers. Builds from packaged artifacts could miss the required header.

Checks

• cd cuda_core && uv run --no-project --with build python -m build --sdist --outdir ../cuda-python-package-check
• tar -tzf ../cuda-python-package-check/cuda_core-*.tar.gz | rg "cuda/core/_cpp/tensor_map_cccl\.h$"
• cd cuda_core && uv run --no-project --with "setuptools>=80" --with "setuptools-scm[simple]>=8" --with "Cython>=3.2,<3.3" --with "cuda-pathfinder>=1.5" python setup.py build_py --build-lib ../cuda-python-build-py-check
• test -f ../cuda-python-build-py-check/cuda/core/_cpp/tensor_map_cccl.h
• git diff --check -- cuda_core/MANIFEST.in cuda_core/pyproject.toml

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.