Add image selection refinement functionality with BEN2 integration

- Implemented viewport.py for handling 3D view projections, gestures, and overlay drawing.
- Created refine_image_selection.py to manage the refinement of gesture masks and output image bounds.
- Added selection module with refine_selection.py to process and crop images based on alpha channel visibility.
- Introduced __init__.py for selection module to expose refine_selection function.

tests/test_clipboard_image.py

@@ -453,6 +453,28 @@ class ClipboardImageTest(unittest.TestCase):
 
         self.assertIs(result, expected_reference)
 
+    def test_reference_image_uses_drag_and_drop_size(self):
+        reference = SimpleNamespace(select_set=Mock())
+        objects = SimpleNamespace(new=Mock(return_value=reference))
+        context = SimpleNamespace(
+            mode="OBJECT",
+            collection=SimpleNamespace(objects=SimpleNamespace(link=Mock())),
+            selected_objects=(),
+            view_layer=SimpleNamespace(objects=SimpleNamespace(active=None)),
+            region_data=None,
+        )
+        image = SimpleNamespace(name="Clipboard", size=(1920, 1080))
+
+        with patch.object(self.actions.bpy.data, "objects", objects, create=True):
+            result = self.actions.add_reference_image(
+                context,
+                image,
+                location=(1.0, 2.0, 3.0),
+            )
+
+        self.assertIs(result, reference)
+        self.assertEqual(reference.empty_display_size, 5.0)
+
     def test_only_import_as_and_shadeless_are_drawn_for_plane_paste(self):
         operator = self.addon.clipboard_image.PasteClipboardImage()
         drawn_properties = []