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/auth/useCurrentUser.ts

@@ -1,5 +1,4 @@
-import { whenever } from '@vueuse/core'
-import { computed } from 'vue'
+import { computed, watch } from 'vue'
 
 import { useFirebaseAuthActions } from '@/composables/auth/useFirebaseAuthActions'
 import { t } from '@/i18n'
@@ -39,7 +38,12 @@ export const useCurrentUser = () => {
       callback(resolvedUserInfo.value)
     }
 
-    const stop = whenever(resolvedUserInfo, callback)
+    const stop = watch(resolvedUserInfo, (value) => {
+      if (value) {
+        callback(value)
+      }
+    })
+
     return () => stop()
   }