Band a continuous SAP score on its published rating 🟩

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

datatypes/epc/domain/epc.py

@@ -1,3 +1,4 @@
+from decimal import ROUND_HALF_UP, Decimal
 from enum import Enum
 
 
@@ -34,7 +35,14 @@ class Epc(Enum):
 
     @classmethod
     def from_sap_continuous(cls, score: float) -> "Epc":
-        raise NotImplementedError
+        """The band an un-rounded SAP rating is *published* in.
+
+        A dwelling is banded on the integer published on its EPC, which rounds
+        half up (SAP 10.2 §13) — so this is `from_sap_score` over that rounding
+        rather than over Python's half-to-even `round`, which would drop an
+        exact x.5 at a band floor into the band below."""
+        published: int = int(Decimal(score).quantize(Decimal("1"), rounding=ROUND_HALF_UP))
+        return cls.from_sap_score(published)
 
     def sap_lower_bound(self) -> int:
         """The minimum SAP rating in this band — the inverse of