Preserve dataflow layout across SQL edits

src/govoplan_dataflow/backend/service.py

@@ -40,7 +40,12 @@ from govoplan_dataflow.backend.governance import (
     definition_governance_payload,
     require_definition_action,
 )
-from govoplan_dataflow.backend.graph import canonical_graph_payload, definition_hash, validate_graph
+from govoplan_dataflow.backend.graph import (
+    canonical_graph_payload,
+    definition_hash,
+    preserve_compatible_graph_layout,
+    validate_graph,
+)
 from govoplan_dataflow.backend.schemas import (
     DataflowDiagnostic,
     GraphNode,
@@ -488,6 +493,8 @@ def compile_sql_draft(payload: PipelineDraftRequest) -> PipelineSqlResponse:
             payload.sql_text,
             source_nodes=_source_nodes(payload.graph, payload.source_nodes),
         )
+        if payload.graph is not None:
+            graph = preserve_compatible_graph_layout(payload.graph, graph)
     except SqlCompilationError as exc:
         return PipelineSqlResponse(
             valid=False,