Fix space regen doubling Z location

Removing translate_obj_to_z_location from the existing-IfcSpace
regeneration branch. The ShapeBuilder rewrite (d8de62308) builds
geometry in local space preserving obj.matrix_world, making the
translate call redundant — it adds z on top of the already-correct
location.z, producing 2*z.

Add test_regenerate_space_preserves_z_location to cover the
regeneration path with a non-zero Z elevation.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/core/spatial.py

@@ -222,7 +222,6 @@ def generate_space(
 
     if element and element.is_a("IfcSpace"):
         spatial.set_space_representation_from_polygon(active_obj, element, space_polygon, h, polygon_is_si=True)
-        spatial.translate_obj_to_z_location(active_obj, z)
     else:
         if relating_type:
             name = model.generate_occurrence_name(relating_type, "IfcSpace")

src/bonsai/test/tool/test_spatial.py

@@ -288,3 +288,27 @@ class TestGenerateSpace(NewFile):
             )
         )
         assert np.allclose(TEST_VERTS, sorted([tuple(v.co) for v in mesh.vertices]))
+
+    def test_regenerate_space_preserves_z_location(self):
+        bpy.ops.bim.create_project()
+        ifc = tool.Ifc.get()
+        scene = bpy.context.scene
+        product = ifcopenshell.api.root.create_entity(ifc, ifc_class="IfcWall")
+        bpy.ops.mesh.primitive_cube_add(size=10, location=(0, 0, 4))
+        obj = bpy.data.objects["Cube"]
+        scene.collection.objects.link(obj)
+        tool.Ifc.link(product, obj)
+        scene.cursor.location = (0, 0, 0)
+
+        bpy.ops.bim.generate_space()
+        space = bpy.data.objects["IfcSpace/Space"]
+        space.location.z = 5
+        bpy.context.view_layer.update()
+
+        bpy.context.view_layer.objects.active = space
+        space.select_set(True)
+        obj.select_set(False)
+
+        bpy.ops.bim.generate_space()
+
+        assert np.isclose(space.location.z, 5), f"Expected z=5, got {space.location.z}"