Add opt-in toggle to join coplanar surface boundaries in drawings

Introduces a "Join Coplanar Surfaces" boolean property (default off)
nested under the "Generate Material Layers" option in BIM_PT_camera.
When enabled, remove_coplanar_boundary_lines runs after linework
generation to suppress shared boundary lines between adjacent coplanar
elements of the same material.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/module/drawing/operator.py

@@ -1005,14 +1005,16 @@ class CreateDrawing(bpy.types.Operator):
             if self.cprops.generate_material_layers:
                 self.generate_material_layers(context, root)
             self.merge_linework_and_add_metadata(root)
-            self.remove_coplanar_boundary_lines(root)
+            if self.cprops.generate_material_layers and self.cprops.join_coplanar_surfaces:
+                self.remove_coplanar_boundary_lines(root)
             self.move_elements_to_top(root)
         elif self.cprops.cut_mode == "OPENCASCADE":
             self.move_projection_to_bottom(root)
             if self.cprops.generate_material_layers:
                 self.generate_material_layers(context, root)
             self.merge_linework_and_add_metadata(root)
-            self.remove_coplanar_boundary_lines(root)
+            if self.cprops.generate_material_layers and self.cprops.join_coplanar_surfaces:
+                self.remove_coplanar_boundary_lines(root)
             self.move_elements_to_top(root)
 
         if self.cprops.fill_mode == "SHAPELY":

src/bonsai/bonsai/bim/module/drawing/prop.py

@@ -500,6 +500,11 @@ class BIMCameraProperties(PropertyGroup):
     generate_material_layers: bpy.props.BoolProperty(
         name="Generate Material Layers", description="Generate material layer linework in drawings", default=True
     )
+    join_coplanar_surfaces: bpy.props.BoolProperty(
+        name="Join Coplanar Surfaces",
+        description="Remove shared boundary lines between adjacent coplanar elements of the same material",
+        default=False,
+    )
     fill_mode: EnumProperty(
         items=[
             ("NONE", "None", "Disable filling areas seen in projection"),

src/bonsai/bonsai/bim/module/drawing/ui.py

@@ -104,6 +104,10 @@ class BIM_PT_camera(Panel):
         row.prop(props, "linework_mode")
         row = self.layout.row()
         row.prop(props, "generate_material_layers")
+        if props.generate_material_layers:
+            row = self.layout.row()
+            row.separator(factor=1.0)
+            row.prop(props, "join_coplanar_surfaces")
         if props.linework_mode == "OPENCASCADE":
             row = self.layout.row()
             row.prop(props, "fill_mode")