refactor: remove unneeded import from cuda/core/__init__.py - #1463

… copy from the merged wheel

build_hooks.py maps a Cython module to its C++ by name. It now also accepts
a directory: every .cpp under cuda/core/_cpp/<stem>/ compiles into the one
extension for _<stem>.pyx, with the legacy single file _cpp/<stem>.cpp kept
as the fallback (tensor_map is unchanged). With no such directory in the
tree yet, the sources are exactly today's, so this part is inert on its own.
The cuda.core._cpp package-data globs become recursive so headers in nested
directories ship, and .gitignore stops ignoring .cpp files under
cuda/core/_cpp/ so new sources are visible to git.

ci/tools/merge_cuda_core_wheels.py stops retaining a third, top-level copy
of _resource_handles and the top-level _cpp/ and _include/ headers in the
merged cu12+cu13 wheel. cuda/core/__init__.py rewrites __path__ to the
versioned subpackage before any import reaches them, so that copy (about
308 KB uncompressed in the 1.2.0 wheel) was never imported; the comment
defending it referred to an import removed in NVIDIA#1463. A step in
build-wheel.yml now asserts that the merged wheel's top level holds only
__init__.py, _version.py and the two versioned trees.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

… copy from the merged wheel (#2799)

* cuda.core: directory-aware C++ build rule and drop the dead top-level copy from the merged wheel

build_hooks.py maps a Cython module to its C++ by name. It now also accepts
a directory: every .cpp under cuda/core/_cpp/<stem>/ compiles into the one
extension for _<stem>.pyx, with the legacy single file _cpp/<stem>.cpp kept
as the fallback (tensor_map is unchanged). With no such directory in the
tree yet, the sources are exactly today's, so this part is inert on its own.
The cuda.core._cpp package-data globs become recursive so headers in nested
directories ship, and .gitignore stops ignoring .cpp files under
cuda/core/_cpp/ so new sources are visible to git.

ci/tools/merge_cuda_core_wheels.py stops retaining a third, top-level copy
of _resource_handles and the top-level _cpp/ and _include/ headers in the
merged cu12+cu13 wheel. cuda/core/__init__.py rewrites __path__ to the
versioned subpackage before any import reaches them, so that copy (about
308 KB uncompressed in the 1.2.0 wheel) was never imported; the comment
defending it referred to an import removed in #1463. A step in
build-wheel.yml now asserts that the merged wheel's top level holds only
__init__.py, _version.py and the two versioned trees.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* cuda.core: keep the merged-wheel layout check in the merge script; use pathlib

Review follow-up. The top-level layout assertion moves from build-wheel.yml
into ci/tools/merge_cuda_core_wheels.py, which now derives the kept cuNN
directories from its input wheels and raises if anything else remains under
cuda/core/ after the removal. _extension_sources uses pathlib.

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>