fix: use ELK partitioning to enforce DO_TRY section order

Invisible ordering edges caused horizontal layout. Replace with ELK's
partitioning feature which explicitly assigns sections to ordered layers:
try_body (partition 0) → doFinally (1) → doCatch (2).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java

@@ -356,12 +356,6 @@ public class ElkDiagramRenderer implements DiagramRenderer {
             allEdges.addAll(collectAllEdges(hr));
         }
         for (ElkEdge elkEdge : allEdges) {
-            // Skip invisible ordering edges used only for DO_TRY section layout
-            String edgeId = elkEdge.getIdentifier();
-            if (edgeId != null && edgeId.startsWith("__ordering_")) {
-                continue;
-            }
-
             String sourceId = elkEdge.getSources().isEmpty() ? "" : elkEdge.getSources().get(0).getIdentifier();
             String targetId = elkEdge.getTargets().isEmpty() ? "" : elkEdge.getTargets().get(0).getIdentifier();
 
@@ -556,6 +550,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
             elkNode.setHeight(100);
             elkNode.setProperty(CoreOptions.ALGORITHM, "org.eclipse.elk.layered");
             elkNode.setProperty(CoreOptions.DIRECTION, Direction.DOWN);
+            elkNode.setProperty(CoreOptions.PARTITIONING_ACTIVATE, true);
             elkNode.setProperty(CoreOptions.SPACING_NODE_NODE, NODE_SPACING * 0.4);
             elkNode.setProperty(CoreOptions.SPACING_EDGE_NODE, EDGE_SPACING * 0.3);
             elkNode.setProperty(CoreOptions.PADDING,
@@ -573,8 +568,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
                 }
             }
 
-            // Virtual _TRY_BODY wrapper with LR direction for horizontal try body chain
+            // Virtual _TRY_BODY wrapper (partition 0 = top)
-            // Layer constraint FIRST ensures it stays at the top of the DO_TRY
             if (!tryBodyChildren.isEmpty()) {
                 String wrapperId = rn.getId() + "._try_body";
                 ElkNode wrapper = factory.createElkNode();
@@ -588,6 +582,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
                 wrapper.setProperty(CoreOptions.SPACING_EDGE_NODE, EDGE_SPACING * 0.5);
                 wrapper.setProperty(CoreOptions.PADDING,
                         new org.eclipse.elk.core.math.ElkPadding(8, 8, 8, 8));
+                wrapper.setProperty(CoreOptions.PARTITIONING_PARTITION, 0);
                 compoundNodeIds.add(wrapperId);
                 elkNodeMap.put(wrapperId, wrapper);
 
@@ -598,12 +593,16 @@ public class ElkDiagramRenderer implements DiagramRenderer {
                 }
             }
 
-            // Handler children: DO_FINALLY in the middle, DO_CATCH at the bottom
+            // DO_FINALLY in the middle (partition 1), DO_CATCH at the bottom (partition 2)
             for (RouteNode child : handlerChildren) {
                 if (child.getType() == NodeType.DO_FINALLY) {
                     childNodeIds.add(child.getId());
                     createElkNodeRecursive(child, elkNode, factory, elkNodeMap, nodeColors,
                             compoundNodeIds, childNodeIds, doTryNodeIds);
+                    ElkNode finallyElk = elkNodeMap.get(child.getId());
+                    if (finallyElk != null) {
+                        finallyElk.setProperty(CoreOptions.PARTITIONING_PARTITION, 1);
+                    }
                 }
             }
             for (RouteNode child : handlerChildren) {
@@ -611,31 +610,11 @@ public class ElkDiagramRenderer implements DiagramRenderer {
                     childNodeIds.add(child.getId());
                     createElkNodeRecursive(child, elkNode, factory, elkNodeMap, nodeColors,
                             compoundNodeIds, childNodeIds, doTryNodeIds);
+                    ElkNode catchElk = elkNodeMap.get(child.getId());
+                    if (catchElk != null) {
+                        catchElk.setProperty(CoreOptions.PARTITIONING_PARTITION, 2);
                     }
                 }
-
-            // Create invisible ordering edges to enforce top-to-bottom:
-            // try_body → doFinally → doCatch
-            List<ElkNode> orderedSections = new ArrayList<>();
-            if (!tryBodyChildren.isEmpty()) {
-                orderedSections.add(elkNodeMap.get(rn.getId() + "._try_body"));
-            }
-            for (RouteNode child : handlerChildren) {
-                if (child.getType() == NodeType.DO_FINALLY) {
-                    orderedSections.add(elkNodeMap.get(child.getId()));
-                }
-            }
-            for (RouteNode child : handlerChildren) {
-                if (child.getType() == NodeType.DO_CATCH) {
-                    orderedSections.add(elkNodeMap.get(child.getId()));
-                }
-            }
-            for (int i = 0; i < orderedSections.size() - 1; i++) {
-                ElkEdge orderEdge = factory.createElkEdge();
-                orderEdge.setIdentifier("__ordering_" + rn.getId() + "_" + i);
-                orderEdge.setContainingNode(elkNode);
-                orderEdge.getSources().add(orderedSections.get(i));
-                orderEdge.getTargets().add(orderedSections.get(i + 1));
             }
         } else if (isCompound) {
             compoundNodeIds.add(rn.getId());