fix: improve DO_TRY diagram layout and node text clipping

- Use NETWORK_SIMPLEX placement for vertical centering of root flow nodes
- Skip structural edges from all compound nodes to descendants (not just DO_TRY)
- Reduce DO_TRY section spacing from NODE_SPACING*0.4 to fixed 20px
- Use SVG clipPath for node text instead of character-count truncation

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

@@ -292,11 +292,11 @@ public class ElkDiagramRenderer implements DiagramRenderer {
         root.setProperty(CoreOptions.HIERARCHY_HANDLING, HierarchyHandling.INCLUDE_CHILDREN);
         root.setProperty(CoreOptions.EDGE_ROUTING, EdgeRouting.POLYLINE);
         root.setProperty(org.eclipse.elk.alg.layered.options.LayeredOptions.NODE_PLACEMENT_STRATEGY,
-                NodePlacementStrategy.LINEAR_SEGMENTS);
+                NodePlacementStrategy.NETWORK_SIMPLEX);
         return root;
     }
 
-    /** Create ELK edges, skipping DO_TRY-to-descendant and cross-root edges. */
+    /** Create ELK edges, skipping structural compound-to-child edges and cross-root edges. */
     private void createElkEdges(RouteGraph graph, LayoutContext ctx) {
         if (graph.getEdges() == null) return;
         for (RouteEdge re : graph.getEdges()) {
@@ -304,8 +304,9 @@ public class ElkDiagramRenderer implements DiagramRenderer {
             ElkNode targetElk = ctx.elkNodeMap.get(re.getTarget());
             if (sourceElk == null || targetElk == null) continue;
 
-            // Skip edges from DO_TRY to its own children (keep continuation edges)
-            if (ctx.doTryNodeIds.contains(re.getSource()) && isDescendantOf(targetElk, sourceElk)) {
+            // Skip edges from any compound node to its own descendants
+            // (these are structural edges, not flow edges)
+            if (ctx.compoundNodeIds.contains(re.getSource()) && isDescendantOf(targetElk, sourceElk)) {
                 continue;
             }
             // Skip edges that cross ELK root boundaries
@@ -334,7 +335,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
             if (sections.size() < 2) continue;
 
             double startY = sections.stream().mapToDouble(ElkNode::getY).min().orElse(0);
-            double spacing = NODE_SPACING * 0.4;
+            double spacing = 20;
             double currentY = startY;
             for (ElkNode section : sections) {
                 section.setY(currentY);