feat(modelling): planning-restriction gate on solid-wall insulation

Slice 2c. recommend_solid_wall takes a PlanningRestrictions value object
(defaults unrestricted): a conservation area removes the EWI Option (external
appearance), a listed or heritage building removes both EWI and IWI (protected
fabric) -> None when nothing survives (ADR-0019). Plus a guard that a cavity
wall yields no solid-wall Recommendation (it is handled by recommend_cavity
_wall). PlanningRestrictions will be sourced onto the Property from the
geospatial layer in slice 3 (ADR-0020).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

domain/modelling/generators/solid_wall_recommendation.py

@@ -15,6 +15,7 @@ generator. Detection + pricing only; impact is produced later by scoring
 (ADR-0016).
 """
 
+from dataclasses import dataclass
 from typing import Final, Optional
 
 from datatypes.epc.domain.epc_property_data import (
@@ -29,6 +30,27 @@ from repositories.product.product_repository import ProductRepository
 _EXTERNAL_MEASURE_TYPE: Final[str] = "external_wall_insulation"
 _INTERNAL_MEASURE_TYPE: Final[str] = "internal_wall_insulation"
 
+
+@dataclass(frozen=True)
+class PlanningRestrictions:
+    """A Property's planning protections that gate wall insulation (ADR-0019).
+    A conservation area blocks EWI only (external appearance); a listed or
+    heritage building blocks both EWI and IWI (protected fabric). Sourced from
+    the geospatial layer onto the Property in a later slice (ADR-0020); defaults
+    to unrestricted."""
+
+    in_conservation_area: bool = False
+    is_listed: bool = False
+    is_heritage: bool = False
+
+    @property
+    def blocks_external(self) -> bool:
+        return self.in_conservation_area or self.is_listed or self.is_heritage
+
+    @property
+    def blocks_internal(self) -> bool:
+        return self.is_listed or self.is_heritage
+
 # RdSAP `wall_construction` codes (consistent across paths for 1-5).
 _WALL_SOLID_BRICK: Final[int] = 3
 _WALL_TIMBER_FRAME: Final[int] = 5
@@ -87,11 +109,22 @@ def _solid_wall_option(
     )
 
 
+def _allowed(measure_type: str, restrictions: PlanningRestrictions) -> bool:
+    """Whether a planning-gated Option survives (ADR-0019): EWI is removed by any
+    restriction; IWI only by a listed/heritage protection."""
+    if measure_type == _EXTERNAL_MEASURE_TYPE:
+        return not restrictions.blocks_external
+    return not restrictions.blocks_internal
+
+
 def recommend_solid_wall(
-    epc: EpcPropertyData, products: ProductRepository
+    epc: EpcPropertyData,
+    products: ProductRepository,
+    restrictions: PlanningRestrictions = PlanningRestrictions(),
 ) -> Optional[Recommendation]:
     """Return a solid-wall insulation Recommendation for an uninsulated, suitable
-    main wall — its constructable EWI/IWI Options — else None."""
+    main wall — its constructable EWI/IWI Options, minus any the Property's
+    planning protections forbid — else None."""
     main = next(
         part
         for part in epc.sap_building_parts
@@ -108,8 +141,15 @@ def recommend_solid_wall(
     if not measure_types:
         return None
 
-    options = tuple(
-        _solid_wall_option(epc, products, measure_type)
+    allowed = tuple(
+        measure_type
         for measure_type in measure_types
+        if _allowed(measure_type, restrictions)
+    )
+    if not allowed:
+        return None
+
+    options = tuple(
+        _solid_wall_option(epc, products, measure_type) for measure_type in allowed
     )
     return Recommendation(surface="Main wall", options=options)

tests/domain/modelling/test_elmhurst_cascade_pins.py

@@ -28,6 +28,7 @@ from domain.modelling.generators.roof_recommendation import recommend_loft_insul
 from domain.modelling.simulation import BuildingPartOverlay, EpcSimulation
 from domain.modelling.generators.wall_recommendation import recommend_cavity_wall
 from domain.modelling.generators.solid_wall_recommendation import (
+    PlanningRestrictions,
     recommend_solid_wall,
 )
 from domain.modelling.recommendation import MeasureOption
@@ -194,6 +195,49 @@ def test_timber_frame_generator_offers_iwi_only_pinning_its_after() -> None:
     )
 
 
+def test_conservation_area_drops_ewi_but_keeps_iwi() -> None:
+    # Arrange — a conservation area blocks the external-appearance change only.
+    before: EpcPropertyData = parse_recommendation_summary(
+        "solid_brick_ewi_001431_before.pdf"
+    )
+
+    # Act
+    recommendation: Recommendation | None = recommend_solid_wall(
+        before, _AnyProduct(), PlanningRestrictions(in_conservation_area=True)
+    )
+
+    # Assert — IWI survives, EWI is gone.
+    assert recommendation is not None
+    assert {option.measure_type for option in recommendation.options} == {
+        "internal_wall_insulation"
+    }
+
+
+def test_listed_building_blocks_all_solid_wall_insulation() -> None:
+    # Arrange — listed/heritage protect the fabric, so both EWI and IWI go.
+    before: EpcPropertyData = parse_recommendation_summary(
+        "solid_brick_ewi_001431_before.pdf"
+    )
+
+    # Act / Assert
+    assert (
+        recommend_solid_wall(
+            before, _AnyProduct(), PlanningRestrictions(is_listed=True)
+        )
+        is None
+    )
+
+
+def test_cavity_wall_gets_no_solid_wall_recommendation() -> None:
+    # Arrange — a cavity wall is handled by recommend_cavity_wall, never here.
+    before: EpcPropertyData = parse_recommendation_summary(
+        "cavity_wall_001431_before.pdf"
+    )
+
+    # Act / Assert
+    assert recommend_solid_wall(before, _AnyProduct()) is None
+
+
 def test_loft_overlay_reproduces_the_relodged_after() -> None:
     # Arrange
     before: EpcPropertyData = parse_recommendation_summary(