Add comprehensive tests for edge depth extension, empty image edits, and material view adaptation

- Introduced `test_edge_depth.py` to validate the functionality of edge depth extension, ensuring core alpha preservation, proper depth handling, and edge padding behavior.
- Created `test_empty_image_edits.py` to verify the behavior of image edits in Blender, focusing on shared edits, preservation of image properties, and handling of failed operations.
- Developed `test_material_view_adaptation.py` to test material adaptation preferences, ensuring color space and alpha settings are correctly applied and preserved across various scenarios.

tests/test_cutout_geometry.py

@@ -331,15 +331,14 @@ def test_cutout_crop_bounds_map_to_the_source_plane():
     np.testing.assert_allclose(bounds, (-0.5, 0.5, -0.25, 0.25))
 
 
-def test_depth_surface_cutout_uses_half_alpha_boundary():
+def test_depth_surface_cutout_uses_default_alpha_boundary():
     alpha = np.zeros((12, 16), dtype=np.float32)
-    alpha[2:10, 2:14] = 0.49
-    alpha[4:8, 5:11] = 0.51
+    alpha[2:10, 2:14] = 0.89
+    alpha[4:8, 5:11] = 0.91
 
     selection_contours = cutout_geometry.extract_cutout_contours(
         alpha,
         64,
-        threshold=0.5,
     )
     contour = np.asarray(selection_contours.components[0][0])
 
@@ -348,6 +347,28 @@ def test_depth_surface_cutout_uses_half_alpha_boundary():
     np.testing.assert_allclose(contour.max(axis=0), (11.0, 8.0))
 
 
+def test_cutout_threshold_controls_contour_and_calibration():
+    alpha = np.zeros((12, 16), dtype=np.float32)
+    alpha[2:10, 2:14] = 0.2
+    alpha[4:8, 5:11] = 1.0
+    for threshold, lower, upper in [
+        (0.0, (2, 2), (14, 10)),
+        (0.1, (2, 2), (14, 10)),
+        (0.5, (5, 4), (11, 8)),
+        (1.0, (5, 4), (11, 8)),
+    ]:
+        contours = cutout_geometry.extract_cutout_contours(
+            alpha, 64, threshold=threshold
+        )
+        contour = np.asarray(contours.components[0][0])
+        np.testing.assert_allclose(contour.min(axis=0), lower)
+        np.testing.assert_allclose(contour.max(axis=0), upper)
+        valid, _ = cutout_geometry.selection_calibration(
+            alpha, alpha.shape, threshold=threshold
+        )
+        np.testing.assert_array_equal(valid, (alpha > 0) & (alpha >= threshold))
+
+
 def test_blender_cutout_alpha_pipeline_does_not_import_pillow():
     original_import = builtins.__import__