Backport pending-opening-cuts banner from gh8088

Extract the pending_opening_recut tracking, three operators (apply /
dismiss / select), Project-panel banner, and the sibling
multi-instance warning banner (its backend helpers already landed
on this branch) from commit a85ed6032 on gizmos-8088.

All tool.* dependencies (Geometry.reimport_element_representations,
Blender.set_objects_selection, Array.*) and IfcImporter.gross_elements
are already on this branch -- no other diffs from a85ed6032 are
pulled.

The source's narrow except-tuple paraphrase comments are trimmed
to keep only the durable "don't swallow programmer errors" note,
per CLAUDE.md s4a.

Tests: 5 bim-lane tests in test/bim/module/project/
test_pending_opening_cuts.py covering apply happy-path + missing
entity, dismiss, select happy-path + cancellation.

Generated with the assistance of an AI coding tool.

src/bonsai/test/bim/module/project/__init__.py

@@ -0,0 +1,19 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.

src/bonsai/test/bim/module/project/test_pending_opening_cuts.py

@@ -0,0 +1,108 @@
+# Bonsai - OpenBIM Blender Add-on
+# Copyright (C) 2026
+#
+# This file is part of Bonsai.
+#
+# Bonsai is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Bonsai is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Bonsai.  If not, see <http://www.gnu.org/licenses/>.
+#
+# This file was generated with the assistance of an AI coding tool.
+
+from unittest.mock import patch
+
+import bpy
+import ifcopenshell
+import pytest
+
+import bonsai.tool as tool
+from test.bim.bootstrap import NewIfc
+
+pytestmark = pytest.mark.project
+
+
+def _populate_pending(*element_ids: int) -> None:
+    pending = tool.Project.get_project_props().pending_opening_recut
+    pending.clear()
+    for eid in element_ids:
+        pending.add().ifc_definition_id = eid
+
+
+def _make_linked_wall(name: str = "Wall") -> tuple[ifcopenshell.entity_instance, bpy.types.Object]:
+    ifc_file = tool.Ifc.get()
+    element = ifc_file.create_entity("IfcWall", GlobalId=ifcopenshell.guid.new(), Name=name)
+    obj = bpy.data.objects.new(name, bpy.data.meshes.new(name))
+    bpy.context.scene.collection.objects.link(obj)
+    tool.Ifc.link(element, obj)
+    return element, obj
+
+
+class TestApplyPendingOpeningCuts(NewIfc):
+    def test_clears_pending_and_calls_reimport_with_apply_openings(self):
+        element, obj = _make_linked_wall()
+        _populate_pending(element.id())
+
+        with patch.object(tool.Geometry, "reimport_element_representations") as mock_reimport, patch(
+            "ifcopenshell.util.representation.get_representation",
+            return_value=object(),
+        ):
+            result = bpy.ops.bim.apply_pending_opening_cuts()
+
+        assert result == {"FINISHED"}
+        assert len(tool.Project.get_project_props().pending_opening_recut) == 0
+        mock_reimport.assert_called_once()
+        _, kwargs = mock_reimport.call_args
+        assert kwargs.get("apply_openings") is True
+
+    def test_skips_entries_whose_entity_is_gone(self):
+        _populate_pending(99999)  # ID guaranteed not present
+
+        with patch.object(tool.Geometry, "reimport_element_representations") as mock_reimport:
+            result = bpy.ops.bim.apply_pending_opening_cuts()
+
+        assert result == {"FINISHED"}
+        assert len(tool.Project.get_project_props().pending_opening_recut) == 0
+        mock_reimport.assert_not_called()
+
+
+class TestDismissPendingOpeningCuts(NewIfc):
+    def test_clears_collection_without_calling_reimport(self):
+        element, _obj = _make_linked_wall()
+        _populate_pending(element.id())
+
+        with patch.object(tool.Geometry, "reimport_element_representations") as mock_reimport:
+            result = bpy.ops.bim.dismiss_pending_opening_cuts()
+
+        assert result == {"FINISHED"}
+        assert len(tool.Project.get_project_props().pending_opening_recut) == 0
+        mock_reimport.assert_not_called()
+
+
+class TestSelectPendingOpeningCuts(NewIfc):
+    def test_selects_objects_for_each_pending_entry(self):
+        e1, o1 = _make_linked_wall("WallA")
+        e2, o2 = _make_linked_wall("WallB")
+        _populate_pending(e1.id(), e2.id())
+
+        for obj in bpy.context.view_layer.objects:
+            obj.select_set(False)
+
+        result = bpy.ops.bim.select_pending_opening_cuts()
+
+        assert result == {"FINISHED"}
+        assert o1.select_get() and o2.select_get()
+        assert bpy.context.view_layer.objects.active in (o1, o2)
+
+    def test_cancels_when_no_objects_match(self):
+        _populate_pending(99999)
+        result = bpy.ops.bim.select_pending_opening_cuts()
+        assert result == {"CANCELLED"}