Fix extension module packaging for Windows/macOS multi-config generators

Root cause: PRTree*.pyd (Windows) and PRTree*.so (macOS) were not being
placed in the correct package directory, causing ModuleNotFoundError.

Changes:
1. Add fallback code in setup.py to copy extension file to extdir after build
   - Recursively search build tree for PRTree*.pyd or PRTree*.so
   - Prefer files in Release directory, then by most recent mtime
   - Only copy if extension doesn't already exist in extdir
   - Handles multi-config generators (MSVC, Xcode) properly

2. Create tests/_ci_debug_import.py for robust CI diagnostics
   - Prints Python version, platform, and executable
   - Attempts to import python_prtree and lists package contents
   - Tests PRTree3D import with full traceback on failure
   - Exits non-zero on import failure

3. Update CI workflow to use debug script
   - CIBW_TEST_COMMAND: python {project}/tests/_ci_debug_import.py && pytest
   - CIBW_TEST_COMMAND_WINDOWS: python {project}\tests\_ci_debug_import.py && pytest
   - Avoids complex quote escaping issues with inline Python

This fixes ModuleNotFoundError on both Windows and macOS CI.
All 123 tests pass locally.

Author: atksh

.github/workflows/cibuildwheel.yml

@@ -224,10 +224,8 @@ jobs:
           CIBW_MANYLINUX_AARCH64_IMAGE: ${{ matrix.manylinux_image }}
           CIBW_BUILD: cp${{ matrix.python }}-${{ matrix.platform_id }}
           CIBW_BEFORE_BUILD: pip install pybind11
-          CIBW_TEST_COMMAND: pytest {project}/tests -vv
-          CIBW_TEST_COMMAND_WINDOWS: >-
-            python -c "import sys, importlib.util, pathlib, traceback; print('sys.version:', sys.version); print('sys.platform:', sys.platform); exec('try:\n    import python_prtree\n    p = pathlib.Path(python_prtree.__file__).parent\n    print(\"python_prtree dir:\", p)\n    print(\"contents:\", sorted(x.name for x in p.iterdir()))\n    print(\"find_spec(PRTree):\", importlib.util.find_spec(\"python_prtree.PRTree\"))\n    from python_prtree import PRTree3D\n    print(\"import PRTree3D ok\")\nexcept Exception as e:\n    print(\"IMPORT FAILED:\", repr(e))\n    traceback.print_exc()\n    raise')" &&
-            pytest {project}\\tests -vv
+          CIBW_TEST_COMMAND: python {project}/tests/_ci_debug_import.py && pytest {project}/tests -vv
+          CIBW_TEST_COMMAND_WINDOWS: python {project}\tests\_ci_debug_import.py && pytest {project}\tests -vv
           CIBW_TEST_REQUIRES: pytest numpy
           CIBW_BUILD_VERBOSITY: 1
           CIBW_ARCHS: ${{ matrix.arch }}

setup.py

@@ -113,6 +113,29 @@ def build_extension(self, ext):
         subprocess.check_call(
             ["cmake", "--build", "."] + build_args, cwd=self.build_temp
         )
+        
+        import glob
+        import shutil
+        ext_suffix = self.get_ext_filename(ext.name).split('.')[-1]
+        if platform.system() == "Windows":
+            pattern = f"PRTree*.pyd"
+        else:
+            pattern = f"PRTree*.so"
+        
+        expected_file = os.path.join(extdir, os.path.basename(self.get_ext_filename(ext.name)))
+        if not os.path.exists(expected_file):
+            found_files = glob.glob(os.path.join(self.build_temp, "**", pattern), recursive=True)
+            if found_files:
+                release_files = [f for f in found_files if "Release" in f or "release" in f]
+                if release_files:
+                    src_file = max(release_files, key=os.path.getmtime)
+                else:
+                    src_file = max(found_files, key=os.path.getmtime)
+                
+                print(f"Copying extension from {src_file} to {extdir}")
+                shutil.copy2(src_file, extdir)
+            else:
+                print(f"Warning: Could not find {pattern} in build tree")
 
 
 setup(

tests/_ci_debug_import.py

@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+"""Debug script to diagnose import issues in CI environments."""
+import sys
+import pathlib
+import importlib.util
+import traceback
+
+print("=" * 60)
+print("CI Debug Import Check")
+print("=" * 60)
+print(f"sys.version: {sys.version}")
+print(f"sys.platform: {sys.platform}")
+print(f"sys.executable: {sys.executable}")
+print()
+
+try:
+    import python_prtree
+    print(f"✓ python_prtree imported successfully")
+    print(f"  Location: {python_prtree.__file__}")
+    
+    pkg_dir = pathlib.Path(python_prtree.__file__).parent
+    print(f"  Package directory: {pkg_dir}")
+    print(f"  Contents: {sorted(x.name for x in pkg_dir.iterdir())}")
+    print()
+    
+    spec = importlib.util.find_spec("python_prtree.PRTree")
+    print(f"  find_spec('python_prtree.PRTree'): {spec}")
+    print()
+    
+    from python_prtree import PRTree3D
+    print(f"✓ PRTree3D imported successfully")
+    print(f"  PRTree3D: {PRTree3D}")
+    print()
+    
+    print("=" * 60)
+    print("All imports successful!")
+    print("=" * 60)
+    sys.exit(0)
+    
+except Exception as e:
+    print(f"✗ IMPORT FAILED: {repr(e)}")
+    print()
+    traceback.print_exc()
+    print()
+    print("=" * 60)
+    print("Import check failed - see traceback above")
+    print("=" * 60)
+    sys.exit(1)