A shard with an unexpected extra column still maps to HistoricEpc 🟥

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

tests/repositories/historic_epc/test_historic_epc_s3_repository.py

@@ -144,6 +144,28 @@ def test_malformed_postcode_raises_postcode_not_found():
         repo.get_for_postcode(Postcode("NONSENSE"))
 
 
+def test_shard_with_unexpected_extra_column_still_maps():
+    # Arrange — the upstream dump can gain columns the domain type doesn't
+    # know; mapping must ignore them rather than explode at construction.
+    buffer = StringIO()
+    writer = csv.DictWriter(buffer, fieldnames=_COLS + ["SOMETHING_NEW"])
+    writer.writeheader()
+    row = {col: "" for col in _COLS}
+    row["ADDRESS"] = "47 GORDON ROAD"
+    row["UPRN"] = "100"
+    row["SOMETHING_NEW"] = "surprise"
+    writer.writerow(row)
+    body = gzip.compress(buffer.getvalue().encode())
+    repo = _repo(_FakeBoto(body=body))
+
+    # Act
+    records = repo.get_for_postcode(Postcode("AB33 8AL"))
+
+    # Assert
+    assert records[0].address == "47 GORDON ROAD"
+    assert records[0].uprn == "100"
+
+
 def test_uprn_trailing_dot_zero_is_stripped():
     # Arrange — pandas reads an integer UPRN column written with a decimal as
     # float, so the cell stringifies to "151020766.0"; the domain UPRN must be