Slice S0380.125: map Elmhurst Summary "18 Hour" meter_type to EIGHTEEN_HOUR

The Elmhurst Summary §14.2 Meters section lodges the electricity meter
type as the bare RdSAP enum form "18 Hour", but `_METER_STR_TO_INT`
only carried the legacy "off-peak 18 hour" alias. All 41 P960-format
heating-system fixtures at `sap worksheets/heating systems examples/`
lodge meter_type "18 Hour", so `cert_to_inputs` strict-raised on every
one of them before this slice.

Per RdSAP 10 Specification §17 page 85 (Electricity meter row 10-2):

  > "Electricity meter: Dual/single/10-hour/18-hour/24-hour/unknown"

Per RdSAP 10 §12 page 62:

  > "if the meter is dual 18-hour/24-hour it is 18-hour/24-hour tariff"

So the bare "18 Hour" lodging routes directly to enum 5 (Off-peak 18
hour) → `Tariff.EIGHTEEN_HOUR`, bypassing the §12 Rules 1-4 dispatch
(which only fires for Dual meters that aren't 18-hour or 24-hour).

After this slice the heating-system corpus probe (`/tmp/probe_*.py`
across 41 variants of the same property × different heating systems)
shifts from "32 raises + 7 mapper gaps + 2 emitter gaps" to
"32 cascade-OK + 7 community-heating + 2 underfloor-emitter + 1
cylinder-size 'No Access'". The 32 newly-OK variants surface a
positive ΔSAP cluster (cascade SAP_c > worksheet SAP_c by +0.87..+30
across boiler types) — that residual layer is queued for the next
slice.

Extended handover suite at HEAD post-slice: **829 pass, 0 fail**
(baseline 775 + test_table_12a.py's 54 incl. the new "18 Hour" entry).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

domain/sap10_calculator/tables/table_12a.py

@@ -83,6 +83,11 @@ _METER_STR_TO_INT: Final[dict[str, int]] = {
     "dual": 1,
     "dual (24 hour)": 4,
     "off-peak 18 hour": 5,
+    # RdSAP 10 §17 page 85 row 10-2 lodging form: "18-hour" (Elmhurst
+    # Summary §14.2 surfaces this as the bare "18 Hour"). Per §12
+    # page 62: "if the meter is dual 18-hour/24-hour it is 18-hour/
+    # 24-hour tariff" → enum 5 (EIGHTEEN_HOUR).
+    "18 hour": 5,
     "unknown": 3,
     "": 3,
 }

domain/sap10_calculator/tests/test_table_12a.py

@@ -51,6 +51,13 @@ def test_tariff_enum_has_five_members() -> None:
         ("Dual", Tariff.SEVEN_HOUR),
         ("Dual (24 hour)", Tariff.TWENTY_FOUR_HOUR),
         ("Off-peak 18 hour", Tariff.EIGHTEEN_HOUR),
+        # RdSAP 10 §17 page 85 (Electricity meter row 10-2):
+        # "Dual/single/10-hour/18-hour/24-hour/unknown". The Elmhurst
+        # Summary §14.2 lodges the bare form "18 Hour" (not the
+        # "Off-peak 18 hour" alias above). Per §12 page 62: "if the
+        # meter is dual 18-hour/24-hour it is 18-hour/24-hour tariff",
+        # so the bare lodging routes directly to EIGHTEEN_HOUR.
+        ("18 Hour", Tariff.EIGHTEEN_HOUR),
         # Per Q11b: "Unknown" maps to STANDARD (no off-peak heuristic).
         ("Unknown", Tariff.STANDARD),
         ("", Tariff.STANDARD),