feat: Add Vue node subgraph title button and fix subgraph navigation with vue nodes (#5572)

## Summary
- Adds subgraph title button to Vue node headers (matching LiteGraph
behavior)
- Fixes Vue node lifecycle issues during subgraph navigation and tab
switching
- Extracts reusable `useSubgraphNavigation` composable with
callback-based API
- Adds comprehensive tests for subgraph functionality
- Ensures proper graph context restoration during tab switches



https://github.com/user-attachments/assets/fd4ff16a-4071-4da6-903f-b2be8dd6e672



┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5572-feat-Add-Vue-node-subgraph-title-button-with-lifecycle-management-26f6d73d365081bfbd9cfd7d2775e1ef)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: DrJKL <DrJKL@users.noreply.github.com>

src/composables/graph/useVueNodeLifecycle.ts

@@ -57,10 +57,12 @@ export function useVueNodeLifecycle(isVueNodesEnabled: Ref<boolean>) {
   const isNodeManagerReady = computed(() => nodeManager.value !== null)
 
   const initializeNodeManager = () => {
-    if (!comfyApp.graph || nodeManager.value) return
+    // Use canvas graph if available (handles subgraph contexts), fallback to app graph
+    const activeGraph = comfyApp.canvas?.graph || comfyApp.graph
+    if (!activeGraph || nodeManager.value) return
 
     // Initialize the core node manager
-    const manager = useGraphNodeManager(comfyApp.graph)
+    const manager = useGraphNodeManager(activeGraph)
     nodeManager.value = manager
     cleanupNodeManager.value = manager.cleanup
 
@@ -71,8 +73,8 @@ export function useVueNodeLifecycle(isVueNodesEnabled: Ref<boolean>) {
     nodeSizes.value = manager.nodeSizes
     detectChangesInRAF.value = manager.detectChangesInRAF
 
-    // Initialize layout system with existing nodes
-    const nodes = comfyApp.graph._nodes.map((node: LGraphNode) => ({
+    // Initialize layout system with existing nodes from active graph
+    const nodes = activeGraph._nodes.map((node: LGraphNode) => ({
       id: node.id.toString(),
       pos: [node.pos[0], node.pos[1]] as [number, number],
       size: [node.size[0], node.size[1]] as [number, number]
@@ -80,7 +82,7 @@ export function useVueNodeLifecycle(isVueNodesEnabled: Ref<boolean>) {
     layoutStore.initializeFromLiteGraph(nodes)
 
     // Seed reroutes into the Layout Store so hit-testing uses the new path
-    for (const reroute of comfyApp.graph.reroutes.values()) {
+    for (const reroute of activeGraph.reroutes.values()) {
       const [x, y] = reroute.pos
       const parent = reroute.parentId ?? undefined
       const linkIds = Array.from(reroute.linkIds)
@@ -88,7 +90,7 @@ export function useVueNodeLifecycle(isVueNodesEnabled: Ref<boolean>) {
     }
 
     // Seed existing links into the Layout Store (topology only)
-    for (const link of comfyApp.graph._links.values()) {
+    for (const link of activeGraph._links.values()) {
       layoutMutations.createLink(
         link.id,
         link.origin_id,
@@ -142,7 +144,9 @@ export function useVueNodeLifecycle(isVueNodesEnabled: Ref<boolean>) {
 
   // Watch for Vue nodes enabled state changes
   watch(
-    () => isVueNodesEnabled.value && Boolean(comfyApp.graph),
+    () =>
+      isVueNodesEnabled.value &&
+      Boolean(comfyApp.canvas?.graph || comfyApp.graph),
     (enabled) => {
       if (enabled) {
         initializeNodeManager()