Synthesise reduced-field windows for RdSAP-Schema-19.0 certs 🟩

Add the 19.0 synthesis seam over the shared _synthesise_reduced_field_windows
core (inherited 20.0.0 coefficients, ND glazing -> DG-modal default 2, per
ADR-0028). 19.0 glazed_type codes (1-4,6,7) are a subset of the verified 1-8
space. The 6 rich certs use lodged window_area directly; the windowless 994
synthesise a 4-way N/E/S/W split.

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

datatypes/epc/domain/mapper.py

@@ -1109,8 +1109,28 @@ class EpcPropertyDataMapper:
                 secondary_heating_type=schema.sap_heating.secondary_heating_type,
                 cylinder_insulation_thickness_mm=schema.sap_heating.cylinder_insulation_thickness,
             ),
-            # 19.0 has no per-window list; individual window fields are at schema root
-            sap_windows=[],
+            # ADR-0028: 994/1000 omit sap_windows -> synthesised from the
+            # glazed_area band + TFA via the shared reduced-field core. The 6
+            # rich certs keep their lodged per-window geometry (used directly:
+            # window_width = area, height = 1.0).
+            sap_windows=[
+                SapWindow(
+                    frame_material=None,
+                    glazing_gap=0,
+                    orientation=w.orientation,
+                    window_type=w.window_type,
+                    glazing_type=w.glazing_type,
+                    window_width=_measurement_value(w.window_area),
+                    window_height=1.0,
+                    draught_proofed=False,
+                    window_location=w.window_location,
+                    window_wall_type=0,
+                    permanent_shutters_present=False,
+                )
+                for w in schema.sap_windows
+            ]
+            if schema.sap_windows
+            else _synthesise_19_0_sap_windows(schema),
             sap_energy_source=SapEnergySource(
                 mains_gas=es.mains_gas == "Y",
                 meter_type=str(es.meter_type),
@@ -3156,6 +3176,28 @@ def _synthesise_18_0_sap_windows(schema: RdSapSchema18_0) -> List[SapWindow]:
     )
 
 
+# ADR-0028: multiple_glazing_type "ND" (Not Defined, 50/1000 19.0 certs) → the
+# DG-modal default, as for 18.0/17.1.
+_RDSAP19_0_ND_GLAZING_TYPE: int = 2
+
+
+def _synthesise_19_0_sap_windows(schema: RdSapSchema19_0) -> List[SapWindow]:
+    """ADR-0028 seam: reuses the inherited 20.0.0 coefficients via the shared
+    core (976/1000 band-1 with no measured band-1 windows; only 6 rich certs).
+    19.0 glazed_type codes (observed 1-4, 6, 7) are a subset of 20.0.0's verified
+    1-8 space: route integer codes through the verified cascade; the "ND" string
+    falls back to the DG-modal default. Own seam so 19.0 can diverge."""
+    mgt = schema.multiple_glazing_type
+    glazing_type = (
+        _api_cascade_glazing_type(mgt)
+        if isinstance(mgt, int)
+        else _RDSAP19_0_ND_GLAZING_TYPE
+    )
+    return _synthesise_reduced_field_windows(
+        schema.glazed_area, schema.total_floor_area, glazing_type
+    )
+
+
 # ADR-0028: multiple_glazing_type "ND" (Not Defined, 56/1000 17.1 certs) → the
 # DG-modal default, as for 18.0.
 _RDSAP17_1_ND_GLAZING_TYPE: int = 2