feat: stabilize graph zone containers

tests/test_graph_explorer.py

@@ -422,11 +422,20 @@ def test_registry_serves_graph_explorer_exports(tmp_path: Path) -> None:
         assert "ZONE_NODE_SEEDED_BY_MULTIPLE_ZONES" in page
         assert "ZONE_EDGE_CROSSES_ZONE_BOUNDARY" in page
         assert "zone.diagnostics" in page
+        assert "isZoneContextOnlyEdge" in page
+        assert "isZoneConnectivityEdge" in page
         assert "currentZoneViewState" in page
         assert "normalizeZoneViewState" in page
         assert "zoneDefinitionSet" in page
         assert "zoneDefinitionSets" in page
         assert "fabric-default" in page
+        assert "zoneContainerState" in page
+        assert "ensureZoneContainer" in page
+        assert "packZoneContainers" in page
+        assert "applyZoneContainerLayout" in page
+        assert "layoutZoneSubgraph" in page
+        assert "serializedZoneContainers" in page
+        assert "normalizedZoneContainers" in page
         assert "collapsedZoneSnapshots" in page
         assert "zoneDragState" in page
         assert "startZoneDrag" in page