Fabric unpicked in phase 1 can re-enter phase 2 on post-fabric worth 🟩

Documents behaviour already delivered: phase 2 optimises every group phase 1
did not consume, with signals re-scored against the fabric-applied dwelling,
so glazing skipped on raw-baseline merit re-enters when it closes the target.
Test passed on arrival.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/domain/modelling/test_optimiser_fabric_first.py

@@ -27,6 +27,7 @@ from domain.modelling.scoring.package_scorer import Score
 from domain.modelling.simulation import (
     BuildingPartOverlay,
     EpcSimulation,
+    GlazingOverlay,
     HeatingOverlay,
 )
 from tests.domain.sap10_calculator.worksheet._elmhurst_worksheet_000490 import (
@@ -201,6 +202,64 @@ class _InteractionScorer:
         )
 
 
+_GLAZING_OVERLAY = EpcSimulation(glazing=GlazingOverlay(glazing_type=2))
+
+
+class _GlazingInteractionScorer:
+    """A stub where glazing is worthless on the raw dwelling (+0) but worth +4
+    once the wall is insulated — so phase 1's max-gain fabric pass leaves it
+    out, and only a phase 2 that re-admits unpicked fabric can close the
+    target with it."""
+
+    def score(
+        self, baseline: EpcPropertyData, simulations: Sequence[EpcSimulation]
+    ) -> Score:
+        wall_present = any(
+            part.wall_insulation_type is not None
+            for sim in simulations
+            for part in sim.building_parts.values()
+        )
+        glazing_present = any(sim.glazing is not None for sim in simulations)
+        heating_present = any(sim.heating is not None for sim in simulations)
+        sap = 60.0
+        sap += 5.0 if wall_present else 0.0
+        sap += (4.0 if wall_present else 0.0) if glazing_present else 0.0
+        sap += 10.0 if heating_present else 0.0
+        return Score(
+            sap_continuous=sap, co2_kg_per_yr=0.0, primary_energy_kwh_per_yr=0.0
+        )
+
+
+def test_fabric_unpicked_in_phase_one_can_reenter_phase_two() -> None:
+    # Arrange — glazing loses phase 1 on merit (it scores nothing on the raw
+    # dwelling), but post-wall it is the only affordable way to the target:
+    # the heat pump that could also close it does not fit the leftover budget.
+    groups: list[list[ScoredOption]] = [
+        [_scored("cavity_wall_insulation", gain=5.0, cost=1000.0, overlay=_WALL_OVERLAY)],
+        [_scored("double_glazing", gain=0.0, cost=500.0, overlay=_GLAZING_OVERLAY)],
+        [_scored("air_source_heat_pump", gain=10.0, cost=8000.0, overlay=_HEATING_OVERLAY)],
+    ]
+    scorer = _GlazingInteractionScorer()
+
+    # Act — target 69 (gain 9); budget £5000 keeps the heat pump out of reach
+    # after the wall's £1000.
+    package: OptimisedPackage = optimise_package_fabric_first(
+        groups=groups,
+        scorer=scorer,
+        baseline_epc=build_epc(),
+        budget=5000.0,
+        target_sap=69.0,
+    )
+
+    # Assert — the skipped glazing re-enters on its post-fabric worth: 60 + 5
+    # wall + 4 glazing = 69, target met.
+    assert _selected_types(package) == {
+        "cavity_wall_insulation",
+        "double_glazing",
+    }
+    assert abs(package.score.sap_continuous - 69.0) <= 1e-9
+
+
 def test_phase_two_values_candidates_against_the_post_fabric_dwelling() -> None:
     # Arrange — one heating Recommendation, two Options. The boiler's role-1
     # signal (vs the raw baseline, +10) beats the heat pump's (+8) and it is