- CUDAExtension module names changed from astrai.extension.<name> to astrai.extension.lib.<name>
- Compiled .so files now land in astrai/extension/lib/ instead of alongside Python source
- loader.py imports from .lib.<name> subpackage
- Add astrai/extension/lib/__init__.py to make lib a proper package
- Separates compiled artifacts from Python source for cleaner directory structure
