python: add CSTransform.copy() method

Exposes the existing C++ copy constructor CSTransform(CSTransform*) as a
Python copy() method returning an independent duplicate of the transform.

Signed-off-by: Thorsten Liebig <thorsten.liebig@gmx.de>
Generated-by: Claude Sonnet 4.6

Author: thliebig

python/CSXCAD/CSTransform.pxd

@@ -24,6 +24,7 @@ cdef extern from "CSXCAD/CSTransform.h":
         cdef cppclass _CSTransform "CSTransform":
             _CSTransform() except +
             _CSTransform(_ParameterSet*) except +
+            _CSTransform(_CSTransform*) except +
 
             void Reset()
 

python/CSXCAD/CSTransform.pyx

@@ -64,6 +64,13 @@ cdef class CSTransform:
         self.thisptr = ptr
         CSTransform._instances[<uintptr_t>self.thisptr] = self
 
+    def copy(self):
+        """Return an independent copy of this transform."""
+        cdef CSTransform obj = CSTransform.__new__(CSTransform)
+        obj.thisptr = new _CSTransform(self.thisptr)
+        obj._SetPtr(obj.thisptr)
+        return obj
+
     def Reset(self):
         """
         Reset all transformations.

python/tests/test_CSTransform.py

@@ -100,6 +100,17 @@ def test_multiply_order(self):
         # post-multiply: translation applied before rotation → translate [1,0,0] → [2,0,0] then rotate → [0,2,0]
         self.assertTrue(compare_coords(self.tr.Transform([1, 0, 0]), [0, 2, 0]))
 
+    def test_copy_is_independent(self):
+        self.tr.Translate([1, 2, 3])
+        t2 = self.tr.copy()
+        # same matrix values
+        self.assertTrue((t2.GetMatrix() == self.tr.GetMatrix()).all())
+        # distinct Python and C++ objects
+        self.assertIsNot(t2, self.tr)
+        # modifying the copy does not affect the original
+        t2.Translate([10, 0, 0])
+        self.assertFalse((t2.GetMatrix() == self.tr.GetMatrix()).all())
+
 
 if __name__ == '__main__':
     unittest.main()