Deterministically guard the electric-underfloor descriptions 🟥

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/domain/epc/test_main_heating_guard.py

@@ -19,6 +19,34 @@ def test_guard_resolves_high_heat_retention_storage() -> None:
     assert result is MainHeatingSystemType.ELECTRIC_STORAGE_HIGH_HEAT_RETENTION
 
 
+@pytest.mark.parametrize(
+    ("description", "expected"),
+    [
+        # Electric underfloor dumped into Direct-acting / old storage (ADR-0046).
+        (
+            "Electric Underfloor Heating: In concrete slab (off-peak only)",
+            MainHeatingSystemType.ELECTRIC_UNDERFLOOR_SLAB_OFF_PEAK,
+        ),
+        (
+            "Electric Underfloor Heating: Integrated (storage+direct-acting) (off peak)",
+            MainHeatingSystemType.ELECTRIC_UNDERFLOOR_INTEGRATED,
+        ),
+        (
+            "Electric Underfloor Heating: In screed above insulation (standard or off peak)",
+            MainHeatingSystemType.ELECTRIC_UNDERFLOOR_SCREED,
+        ),
+    ],
+)
+def test_guard_resolves_electric_underfloor(
+    description: str, expected: MainHeatingSystemType
+) -> None:
+    # Act
+    result = main_heating_guard(description)
+
+    # Assert
+    assert result is expected
+
+
 @pytest.mark.parametrize(
     ("description", "expected"),
     [