Refactor depth node groups and simplify options

- Removed `Smooth Weight` input from `O Image Depth Plane`, `O Image Depth Cutout`, and `O Image Depth Panorama` to streamline the interface and maintain consistent boundary smoothing behavior.
- Adjusted the `Reference Depth` input to appear last in the options panel for better organization, reflecting its role as a calibration value.
- Consolidated the `expand_smooth()` function to only accept necessary parameters, eliminating unused branches related to `Smooth Weight` and `pin_sharp`.
- Updated related tests and node assets to ensure functionality remains intact and consistent with the new structure.
- Introduced new specifications to document the changes and ensure compliance with the updated requirements.

tools/nodes/groups/image_relief_plane.py

@@ -55,6 +55,11 @@ def build_image_relief_plane_group(image_plane_group):
     valid_only.description = "Treat depth-mask-invalid areas as zero depth instead of deleting them."
     valid_only.default_value = True
     options = group.interface.new_panel(name="Options", default_closed=True)
+    validity_threshold = _interface_socket(group, "Mask Threshold", "INPUT", "NodeSocketFloat", options)
+    validity_threshold.description = "Set the minimum depth mask value treated as valid."
+    validity_threshold.default_value = 0.9
+    validity_threshold.min_value, validity_threshold.max_value = 0.0, 1.0
+    validity_threshold.subtype = "FACTOR"
     base_plane_depth = _interface_socket(
         group,
         "Reference Depth",
@@ -65,11 +70,6 @@ def build_image_relief_plane_group(image_plane_group):
     base_plane_depth.default_value = 1.0
     base_plane_depth.min_value = 0.0
     base_plane_depth.subtype = "DISTANCE"
-    validity_threshold = _interface_socket(group, "Mask Threshold", "INPUT", "NodeSocketFloat", options)
-    validity_threshold.description = "Set the minimum depth mask value treated as valid."
-    validity_threshold.default_value = 0.9
-    validity_threshold.min_value, validity_threshold.max_value = 0.0, 1.0
-    validity_threshold.subtype = "FACTOR"
     data = group.interface.new_panel(name="Data", default_closed=True)
     uniform_scale = _interface_socket(
         group,