Mapper falls back to legacy trickle vent label for pre-existing API responses 🟥

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/domain/magicplan/test_mapper.py

@@ -8,6 +8,7 @@ import domain.magicplan.api.response as api
 from domain.magicplan.api.response import MagicPlanPlan, Symbol, Vec3, WallItem
 from domain.magicplan.mapper import (
     _map_window,  # pyright: ignore[reportPrivateUsage]
+    _map_window_ventilation,  # pyright: ignore[reportPrivateUsage]
     map_address,
     map_plan,
 )
@@ -229,3 +230,28 @@ def test_map_address_city_absent_is_omitted() -> None:
 
 def test_map_address_none_returns_none() -> None:
     assert map_address(None) is None
+
+
+def _make_survey_field(label: str, value: str) -> api.SurveyField:
+    return api.SurveyField(
+        id="test",
+        type=5,
+        type_as_string="float",
+        is_required=False,
+        label=label,
+        value=api.FieldValue(index=-1, has_value=True, is_array=False, value=value),
+    )
+
+
+def test_trickle_vent_area_read_from_legacy_field_label() -> None:
+    # Arrange — old MagicPlan label, not yet renamed in the API response
+    fields = [_make_survey_field(
+        "Trickle Vent Effective Area (mm2) (No Code Then Width x Height)", "1700"
+    )]
+
+    # Act
+    vent = _map_window_ventilation(fields)
+
+    # Assert
+    assert vent is not None
+    assert vent.trickle_vent_area_mm2 == 1700