refactor(baseline): Performance.from_sap_result replaces the loose mapper

PR feedback: the SapResult -> Performance mapping should be a method, not a
free function you must know exists in the rebaseliner. Put the factory on
the target as `Performance.from_sap_result`, beside its sibling
`lodged_performance` and mirroring `Epc.from_sap_score` (the factory this
mapping already calls).

Not a `SapResult.to_performance()`: that would make the SAP calculator
import `Performance` (a property_baseline type), re-introducing the
engine->consumer coupling removed by the SapCalculator ABC. SapResult is a
TYPE_CHECKING-only import in performance.py (the body only reads attributes),
so the calculator module is not pulled in at runtime.

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

domain/property_baseline/calculator_rebaseliner.py

@@ -3,7 +3,6 @@ from __future__ import annotations
 import logging
 from typing import TYPE_CHECKING, Optional
 
-from datatypes.epc.domain.epc import Epc
 from domain.property_baseline.performance import Performance
 from domain.property_baseline.rebaseliner import Rebaseliner, RebaselineReason
 
@@ -22,17 +21,6 @@ _REL_TOL = 0.01
 _KG_PER_TONNE = 1000.0
 
 
-def performance_from_sap_result(result: "SapResult") -> Performance:
-    """The four rated quantities, read off a `SapResult`: band derived from the
-    score, CO2 converted kg→tonnes, PEUI rounded to the lodged integer scale."""
-    return Performance(
-        sap_score=result.sap_score,
-        epc_band=Epc.from_sap_score(result.sap_score),
-        co2_emissions=result.co2_kg_per_yr / _KG_PER_TONNE,
-        primary_energy_intensity=round(result.primary_energy_kwh_per_m2),
-    )
-
-
 def _relative_diff(calculated: float, lodged: float) -> float:
     if lodged == 0:
         return 0.0 if calculated == 0 else float("inf")
@@ -62,7 +50,7 @@ class CalculatorRebaseliner(Rebaseliner):
         result: SapResult = self._calculator.calculate(effective_epc)
         sap_version: Optional[float] = effective_epc.sap_version
         if sap_version is not None and sap_version < _SAP10_2_FLOOR:
-            return performance_from_sap_result(result), "pre_sap10"
+            return Performance.from_sap_result(result), "pre_sap10"
         self._log_divergence(
             property_id=property_id, sap_version=sap_version, result=result, lodged=lodged
         )

domain/property_baseline/performance.py

@@ -1,12 +1,16 @@
 from __future__ import annotations
 
 from dataclasses import dataclass
-from typing import Optional, TypeVar
+from typing import Optional, TYPE_CHECKING, TypeVar
 
 from datatypes.epc.domain.epc import Epc
 from datatypes.epc.domain.epc_property_data import EpcPropertyData
 
+if TYPE_CHECKING:
+    from domain.sap10_calculator.calculator import SapResult
+
 _T = TypeVar("_T")
+_KG_PER_TONNE = 1000.0
 
 
 @dataclass(frozen=True)
@@ -24,6 +28,20 @@ class Performance:
     co2_emissions: float
     primary_energy_intensity: int
 
+    @classmethod
+    def from_sap_result(cls, result: "SapResult") -> "Performance":
+        """The four rated quantities, read off a calculator `SapResult`
+        (ADR-0013): band derived from the score, CO2 converted kg→tonnes, PEUI
+        rounded to the lodged integer scale. The `from_*` factory mirrors
+        `Epc.from_sap_score`; living on the target keeps the SAP calculator
+        free of any `property_baseline` dependency."""
+        return cls(
+            sap_score=result.sap_score,
+            epc_band=Epc.from_sap_score(result.sap_score),
+            co2_emissions=result.co2_kg_per_yr / _KG_PER_TONNE,
+            primary_energy_intensity=round(result.primary_energy_kwh_per_m2),
+        )
+
 
 def _require(value: Optional[_T], field: str) -> _T:
     if value is None: