Support validated legacy portfolio composition

tests/test_combine_belgium_building_portfolio_specs.py

@@ -36,3 +36,18 @@ def test_combine_specs_rejects_mismatched_resolution(tmp_path: Path) -> None:
 def test_combine_specs_rejects_incomplete_source(tmp_path: Path) -> None:
     with pytest.raises(ValueError, match="not complete"):
         combine_specs([write_spec(tmp_path / "one.json", "one", status="in_progress")])
+
+
+def test_combine_specs_accepts_populated_legacy_v1_when_dimensions_come_from_complete_spec(tmp_path: Path) -> None:
+    legacy = tmp_path / "legacy.json"
+    legacy.write_text(json.dumps({"schema_version": 1, "samples": [{"sample_slug": "legacy"}]}), encoding="utf-8")
+    payload = combine_specs([legacy, write_spec(tmp_path / "current.json", "current")])
+    assert payload["sample_count"] == 2
+    assert payload["source_specs"][0]["source_status"] == "legacy_unstated"
+
+
+def test_combine_specs_rejects_empty_legacy_v1(tmp_path: Path) -> None:
+    legacy = tmp_path / "legacy.json"
+    legacy.write_text(json.dumps({"schema_version": 1, "samples": []}), encoding="utf-8")
+    with pytest.raises(ValueError, match="not complete"):
+        combine_specs([legacy, write_spec(tmp_path / "current.json", "current")])