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.

tools/nodes/common/cutout.py

@@ -3,27 +3,6 @@ from .nodes import math_node
 from anyimage.operators.cutout_tool.shape import BALLOON_ATTRIBUTE_NAME
 
 
-def _island_cleanup(group, geometry, cleanup):
-    nodes = group.nodes
-    links = group.links
-    mesh_island = nodes.new("GeometryNodeInputMeshIsland")
-    face_area = nodes.new("GeometryNodeInputMeshFaceArea")
-    island_area = nodes.new("GeometryNodeAccumulateField")
-    island_area.data_type = "FLOAT"
-    island_area.domain = "FACE"
-    links.new(face_area.outputs["Area"], island_area.inputs["Value"])
-    links.new(mesh_island.outputs["Island Index"], island_area.inputs["Group ID"])
-
-    tiny = math_node(nodes, "LESS_THAN")
-    links.new(island_area.outputs["Total"], tiny.inputs[0])
-    links.new(cleanup, tiny.inputs[1])
-    delete = nodes.new("GeometryNodeDeleteGeometry")
-    delete.domain = "FACE"
-    links.new(geometry, delete.inputs["Geometry"])
-    links.new(tiny.outputs[0], delete.inputs["Selection"])
-    return delete.outputs["Geometry"]
-
-
 def _profile_field(group, geometry):
     nodes = group.nodes
     links = group.links