fix: straight edge routing and handler section edge extraction

Backend:
- Set POLYLINE edge routing on ELK root — eliminates curved/bent edges
  between horizontally aligned nodes
- Collect edges from handler section roots (not just main root) so
  internal handler edges are included in the layout output
- Use correct root reference for coordinate calculation per edge

Frontend:
- Render ALL edge points as line segments (polylines), not cubic bezier.
  ELK bend points are waypoints, not bezier control points — the cubic
  bezier interpretation caused false curves.

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

@@ -12,6 +12,7 @@ import org.eclipse.elk.alg.layered.options.LayeredMetaDataProvider;
 import org.eclipse.elk.core.RecursiveGraphLayoutEngine;
 import org.eclipse.elk.core.options.CoreOptions;
 import org.eclipse.elk.core.options.Direction;
+import org.eclipse.elk.core.options.EdgeRouting;
 import org.eclipse.elk.core.options.HierarchyHandling;
 import org.eclipse.elk.alg.layered.options.NodePlacementStrategy;
 import org.eclipse.elk.core.util.BasicProgressMonitor;
@@ -188,6 +189,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
         rootNode.setProperty(CoreOptions.SPACING_NODE_NODE, NODE_SPACING);
         rootNode.setProperty(CoreOptions.SPACING_EDGE_NODE, EDGE_SPACING);
         rootNode.setProperty(CoreOptions.HIERARCHY_HANDLING, HierarchyHandling.INCLUDE_CHILDREN);
+        rootNode.setProperty(CoreOptions.EDGE_ROUTING, EdgeRouting.POLYLINE);
         rootNode.setProperty(org.eclipse.elk.alg.layered.options.LayeredOptions.NODE_PLACEMENT_STRATEGY,
                 NodePlacementStrategy.LINEAR_SEGMENTS);
 
@@ -305,27 +307,34 @@ public class ElkDiagramRenderer implements DiagramRenderer {
             }
         }
 
-        // Extract edges
+        // Extract edges from main root + all handler roots
         List<PositionedEdge> positionedEdges = new ArrayList<>();
-        for (ElkEdge elkEdge : collectAllEdges(rootNode)) {
+        List<ElkEdge> allEdges = collectAllEdges(rootNode);
+        for (ElkNode hr : handlerRoots) {
+            allEdges.addAll(collectAllEdges(hr));
+        }
+        for (ElkEdge elkEdge : allEdges) {
             String sourceId = elkEdge.getSources().isEmpty() ? "" : elkEdge.getSources().get(0).getIdentifier();
             String targetId = elkEdge.getTargets().isEmpty() ? "" : elkEdge.getTargets().get(0).getIdentifier();
 
+            // Determine which root this edge belongs to for coordinate calculation
+            ElkNode edgeRoot = getElkRoot(elkEdge.getContainingNode());
+
             List<double[]> points = new ArrayList<>();
             for (ElkEdgeSection section : elkEdge.getSections()) {
                 points.add(new double[]{
-                        section.getStartX() + getAbsoluteX(elkEdge.getContainingNode(), rootNode),
-                        section.getStartY() + getAbsoluteY(elkEdge.getContainingNode(), rootNode)
+                        section.getStartX() + getAbsoluteX(elkEdge.getContainingNode(), edgeRoot),
+                        section.getStartY() + getAbsoluteY(elkEdge.getContainingNode(), edgeRoot)
                 });
                 for (ElkBendPoint bp : section.getBendPoints()) {
                     points.add(new double[]{
-                            bp.getX() + getAbsoluteX(elkEdge.getContainingNode(), rootNode),
-                            bp.getY() + getAbsoluteY(elkEdge.getContainingNode(), rootNode)
+                            bp.getX() + getAbsoluteX(elkEdge.getContainingNode(), edgeRoot),
+                            bp.getY() + getAbsoluteY(elkEdge.getContainingNode(), edgeRoot)
                     });
                 }
                 points.add(new double[]{
-                        section.getEndX() + getAbsoluteX(elkEdge.getContainingNode(), rootNode),
-                        section.getEndY() + getAbsoluteY(elkEdge.getContainingNode(), rootNode)
+                        section.getEndX() + getAbsoluteX(elkEdge.getContainingNode(), edgeRoot),
+                        section.getEndY() + getAbsoluteY(elkEdge.getContainingNode(), edgeRoot)
                 });
             }
 

ui/src/components/ProcessDiagram/DiagramEdge.tsx

@@ -11,19 +11,11 @@ export function DiagramEdge({ edge, offsetY = 0, traversed }: DiagramEdgeProps)
   const pts = edge.points;
   if (!pts || pts.length < 2) return null;
 
-  // Build SVG path: move to first point, then cubic bezier or line to rest
+  // Build SVG path: move to first point, then line segments through all waypoints.
+  // ELK bend points are waypoints, not bezier control points.
   let d = `M ${pts[0][0]} ${pts[0][1] + offsetY}`;
-
-  if (pts.length === 2) {
-    d += ` L ${pts[1][0]} ${pts[1][1] + offsetY}`;
-  } else if (pts.length === 4) {
-    // 4 points: start, control1, control2, end → cubic bezier
-    d += ` C ${pts[1][0]} ${pts[1][1] + offsetY}, ${pts[2][0]} ${pts[2][1] + offsetY}, ${pts[3][0]} ${pts[3][1] + offsetY}`;
-  } else {
-    // Multiple points: connect with line segments through intermediate points
-    for (let i = 1; i < pts.length; i++) {
-      d += ` L ${pts[i][0]} ${pts[i][1] + offsetY}`;
-    }
+  for (let i = 1; i < pts.length; i++) {
+    d += ` L ${pts[i][0]} ${pts[i][1] + offsetY}`;
   }
 
   return (