Constrain visible roof grouping to compact clusters

backend/tests/test_building_label_normalization.py

@@ -179,3 +179,25 @@ def test_normalizer_merges_only_touching_visible_roof_instances(tmp_path: Path)
     assert sorted(item["properties"]["source_feature_count"] for item in normalized["features"]) == [1, 2]
     assert audit["accepted_source_feature_count"] == 3
     assert audit["accepted_feature_count"] == 2
+
+
+def test_visible_roof_merge_retains_large_touching_chains() -> None:
+    features = []
+    for index in range(13):
+        left = float(index)
+        features.append(
+            {
+                "type": "Feature",
+                "id": str(index),
+                "properties": {"source_feature_id": str(index)},
+                "geometry": {
+                    "type": "Polygon",
+                    "coordinates": [[[left, 0], [left + 1, 0], [left + 1, 1], [left, 1], [left, 0]]],
+                },
+            }
+        )
+    merged = module.merge_touching_roof_instances(features, "grb")
+    assert len(merged) == 13
+    assert {item["properties"]["label_semantics"] for item in merged} == {
+        "native_instance_complex_touch_group"
+    }