Bonsai: restore opening regen on recalculate_fill

Commit 82dd1d94d switched RecalculateFill from
bonsai.core.geometry.switch_representation to the surgical
tool.Geometry.recut_host to speed up batched host recuts. The trade-off
was intentional for that scope but dropped the implicit opening body
refresh that switch_representation used to provide: SHIFT+G on a door
whose parametric dimensions had drifted from its opening no longer
resized the opening, so the wall recut still hit a stale mapped source.

Extract a targeted single-source helper on tool.Model
(regenerate_filling_opening_body) that regenerates one filling's
mapped opening body via the existing FilledOpeningGenerator and
inverse-substitutes the new representation across every filling that
shares the mapped source. Refactor the family-wide caller
(update_simple_openings, used by the parametric-edit finish path) to
delegate to the same helper, deduped by source id so fragmented type
families where multiple mapped sources coexist all get refreshed.

Call the targeted helper at the top of RecalculateFill._recalculate_fills
for each distinct source among the selected fillings. All body-
representation lookups go through tool.Geometry.get_body_representation
rather than inlining the ("Model", "Body", "MODEL_VIEW") triple. An AST
forward-compat guard pins the call site.

Generated with the assistance of an AI coding tool.

src/bonsai/test/bim/module/model/test_recalculate_fill_forward_compat.py

@@ -0,0 +1,59 @@
+# 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.
+
+"""AST contract: ``RecalculateFill`` must invoke
+``regenerate_simple_opening_bodies`` before recutting hosts.
+
+Hosts recut with a surgical mesh-only path don't refresh the shared mapped
+opening source — so any change to a parametric filling's dimensions stays
+invisible at the opening boundary until the body representation is
+regenerated. Pinning the call site forces future refactors to keep the
+regen step in place."""
+
+import ast
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.model
+
+
+def _recalculate_fill_body_source() -> str:
+    from bonsai.bim.module.model import opening as opening_module
+
+    source = Path(opening_module.__file__).read_text(encoding="utf-8")
+    tree = ast.parse(source)
+    for node in ast.walk(tree):
+        if isinstance(node, ast.ClassDef) and node.name == "RecalculateFill":
+            for child in node.body:
+                if isinstance(child, ast.FunctionDef) and child.name == "_recalculate_fills":
+                    return ast.unparse(child)
+    raise AssertionError("RecalculateFill._recalculate_fills was not found in opening.py")
+
+
+def test_recalculate_fill_regenerates_opening_bodies_before_recut():
+    body = _recalculate_fill_body_source()
+    assert "regenerate_filling_opening_body" in body, (
+        "RecalculateFill._recalculate_fills must call "
+        "tool.Model.regenerate_filling_opening_body for each selected "
+        "filling before recutting the host. Without that call the host is "
+        "recut against a stale shared mapped opening source, so changes "
+        "to filling dimensions never surface."
+    )