Refactor depth reference handling and cleanup

- Unified reference depth calculation to use a single implementation in common/depth.py.
- Removed server-side reference depth computation and adjusted depth.json to only include image_size and intrinsics.
- Updated depth texture handling to ignore transparent, invalid, and non-positive pixels when calculating reference depth.
- Changed reference depth calculation to use the 95th percentile of valid depth values.
- Adjusted depth direction fitting to return a flat direction when no samples are available.
- Removed cleanup threshold parameters from Cutout and related nodes, simplifying the interface.
- Updated tests to verify new reference depth logic and ensure compatibility with existing functionality.

tests/anyimage/operators/test_plane_operators.py

@@ -67,7 +67,10 @@ class PlaneOperatorsTest(BlenderTestCase):
             depth_image = SimpleNamespace(users=0)
             normal_image = SimpleNamespace(users=0)
             material = SimpleNamespace(users=0)
-            metadata = {"reference_depth": 1.0}
+            metadata = {
+                "image_size": (2, 1),
+                "intrinsics": ((1.0, 0.0, 0.0), (0.0, 1.0, 0.0), (0.0, 0.0, 1.0)),
+            }
             files = {
                 "depth_metadata": Path("depth.json"),
                 "depth": Path("depth.exr"),
@@ -153,7 +156,10 @@ class PlaneOperatorsTest(BlenderTestCase):
             patch.object(
                 module,
                 "load_depth_metadata",
-                return_value={"reference_depth": 1.0},
+                return_value={
+                    "image_size": (2, 1),
+                    "intrinsics": ((1.0, 0.0, 0.0), (0.0, 1.0, 0.0), (0.0, 0.0, 1.0)),
+                },
             ),
             patch.object(module, "load_depth_result_image", return_value=depth_image),
             patch.object(module, "load_normal_result_image", return_value=normal_image),