[BUG] CuTeDSL editable install broken: prep_editable_install.py extracts nothing from the split nvidia-cutlass-dsl wheels (>= 4.4.0)

python/CuTeDSL/prep_editable_install.py downloads nvidia-cutlass-dsl with pip download --no-deps. Since 4.4.0 that wheel is a metadata-only shim (nvidia_cutlass_dsl-4.6.1-py3-none-any.whl is ~10 KB: one .pth + dist-info); the actual libraries live in nvidia-cutlass-dsl-libs-{base,core,cu12,cu13} wheels, under dsl_packages/ rather than python_packages/. The script therefore copies nothing — Summary: 0 lib files, 0 Python files copied — but still logs "Setup completed successfully!" and exits 0. The subsequent pip install -e . / setup.sh --editable also succeeds, and the breakage only surfaces at first use: import cutlass → ModuleNotFoundError: No module named 'cutlass._mlir'.

Repro: fresh venv on x86_64/aarch64 Linux, python prep_editable_install.py at any commit since the script landed.

Fix proposal in the linked PR: detect the shim, follow its nvidia-cutlass-dsl-libs-* Requires-Dist for one CUDA variant, merge all payload dirs, error loudly on empty extraction. PR #3204 previously attempted this but is stale and predates the 4.6.x layout (its default base provider no longer contains lib/*.so).

Start in python/CuTeDSL/prep_editable_install.py and reproduce the empty extraction with python prep_editable_install.py in a fresh Linux virtual environment. Inspect the metadata-only nvidia-cutlass-dsl wheel and its nvidia-cutlass-dsl-libs-* Requires-Dist entries, including the 4.6.x dsl_packages layout. Done means the libraries are copied for a CUDA variant, empty extraction fails loudly, and import cutlass succeeds after editable installation.