refactor: simplify ElkDiagramRenderer layout code

- Introduce LayoutContext to bundle 8 accumulator params into 1 object
- Extract computeLayout (261 lines) into 6 focused sub-methods:
  buildNodeIndex, partitionNodes, createElkRoot, createElkEdges,
  postProcessDoTrySections, extractLayout
- Consolidate duplicated DO_TRY handler iteration via orderedHandlerChildren
- De-duplicate ELK root configuration (main + handler roots)
- Add DO_TRY test cases for section ordering and uniform width
- Clean up orphaned Javadoc comments

No behavioral changes. 882 → 841 lines.

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

cameleer3-server-app/src/test/java/com/cameleer3/server/app/diagram/ElkDiagramRendererTest.java

@@ -172,6 +172,98 @@ class ElkDiagramRendererTest {
         assertEquals(2, choiceNode.children().size(), "Choice node should have 2 children (when, otherwise)");
     }
 
+    /**
+     * Build a DO_TRY graph: from -> doTry(try: [process, log], doFinally: [cleanup], doCatch: [errorLog]) -> to
+     */
+    private RouteGraph buildDoTryGraph() {
+        RouteGraph graph = new RouteGraph("try-catch-route");
+        graph.setExtractedAt(Instant.now());
+        graph.setVersion(1);
+
+        RouteNode from = new RouteNode("node-1", NodeType.ENDPOINT, "timer:tick");
+        RouteNode doTry = new RouteNode("node-2", NodeType.DO_TRY, "doTry");
+        RouteNode process = new RouteNode("node-3", NodeType.PROCESSOR, "process");
+        RouteNode log1 = new RouteNode("node-4", NodeType.LOG, "log:tryBody");
+        RouteNode doFinally = new RouteNode("node-5", NodeType.DO_FINALLY, "doFinally");
+        RouteNode cleanup = new RouteNode("node-6", NodeType.LOG, "log:cleanup");
+        RouteNode doCatch = new RouteNode("node-7", NodeType.DO_CATCH, "doCatch");
+        RouteNode errorLog = new RouteNode("node-8", NodeType.LOG, "log:error");
+        RouteNode to = new RouteNode("node-9", NodeType.TO, "log:done");
+
+        doFinally.setChildren(List.of(cleanup));
+        doCatch.setChildren(List.of(errorLog));
+        doTry.setChildren(List.of(process, log1, doFinally, doCatch));
+
+        graph.setRoot(from);
+        graph.setNodes(List.of(from, doTry, process, log1, doFinally, cleanup, doCatch, errorLog, to));
+        graph.setEdges(List.of(
+                new RouteEdge("node-1", "node-2", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-2", "node-3", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-3", "node-4", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-2", "node-5", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-5", "node-6", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-2", "node-7", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-7", "node-8", RouteEdge.EdgeType.FLOW),
+                new RouteEdge("node-2", "node-9", RouteEdge.EdgeType.FLOW)
+        ));
+
+        return graph;
+    }
+
+    @Test
+    void layoutJson_doTryGraph_sectionsInCorrectOrder() {
+        DiagramLayout layout = renderer.layoutJson(buildDoTryGraph());
+
+        assertNotNull(layout);
+
+        // Find the DO_TRY compound node
+        PositionedNode doTryNode = layout.nodes().stream()
+                .filter(n -> "node-2".equals(n.id()))
+                .findFirst()
+                .orElseThrow(() -> new AssertionError("DO_TRY node not found"));
+
+        assertNotNull(doTryNode.children(), "DO_TRY should have children");
+        assertFalse(doTryNode.children().isEmpty(), "DO_TRY should have non-empty children");
+
+        // Find sections by ID pattern
+        PositionedNode tryBody = doTryNode.children().stream()
+                .filter(n -> n.id() != null && n.id().contains("._try_body"))
+                .findFirst().orElse(null);
+        PositionedNode finallySection = doTryNode.children().stream()
+                .filter(n -> "node-5".equals(n.id()))
+                .findFirst().orElse(null);
+        PositionedNode catchSection = doTryNode.children().stream()
+                .filter(n -> "node-7".equals(n.id()))
+                .findFirst().orElse(null);
+
+        assertNotNull(tryBody, "Try body wrapper should exist");
+        assertNotNull(finallySection, "doFinally section should exist");
+        assertNotNull(catchSection, "doCatch section should exist");
+
+        // Verify vertical order: tryBody.y < doFinally.y < doCatch.y
+        assertTrue(tryBody.y() < finallySection.y(),
+                "Try body (y=" + tryBody.y() + ") should be above doFinally (y=" + finallySection.y() + ")");
+        assertTrue(finallySection.y() < catchSection.y(),
+                "doFinally (y=" + finallySection.y() + ") should be above doCatch (y=" + catchSection.y() + ")");
+    }
+
+    @Test
+    void layoutJson_doTryGraph_sectionsHaveSameWidth() {
+        DiagramLayout layout = renderer.layoutJson(buildDoTryGraph());
+
+        PositionedNode doTryNode = layout.nodes().stream()
+                .filter(n -> "node-2".equals(n.id()))
+                .findFirst()
+                .orElseThrow(() -> new AssertionError("DO_TRY node not found"));
+
+        List<PositionedNode> sections = doTryNode.children();
+        double firstWidth = sections.get(0).width();
+        for (PositionedNode section : sections) {
+            assertEquals(firstWidth, section.width(), 0.1,
+                    "All sections should have the same width, but " + section.id() + " differs");
+        }
+    }
+
     @Test
     void renderSvg_compoundGraph_producesValidSvg() {
         String svg = renderer.renderSvg(buildCompoundGraph());