fix restoring outputs in Vue nodes (persisting node outputs when switching between workflow tabs) (#5788)

## Summary

Fixed Vue node output restoration by consolidating state management
through the node output store.

## Changes

- **What**: Refactored node output cleanup and restoration logic in
`ChangeTracker` and `ComfyApp` to use centralized store methods
- **Breaking**: Removed direct manipulation of `app.nodeOutputs` in
favor of store-managed state

## Review Focus

State synchronization between `app.nodeOutputs` and `nodeOutputs.value`
during restore/reset operations, ensuring Vue reactivity is maintained.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5788-fix-restoring-outputs-in-Vue-nodes-persisting-node-outputs-when-switching-between-workfl-27a6d73d365081b39411fed7479d8ac5)
by [Unito](https://www.unito.io)

src/stores/imagePreviewStore.ts

@@ -328,6 +328,19 @@ export const useNodeOutputStore = defineStore('nodeOutput', () => {
     return hadOutputs
   }
 
+  function restoreOutputs(
+    outputs: Record<string, ExecutedWsMessage['output']>
+  ) {
+    app.nodeOutputs = outputs
+    nodeOutputs.value = outputs
+  }
+
+  function resetAllOutputsAndPreviews() {
+    app.nodeOutputs = {}
+    nodeOutputs.value = {}
+    revokeAllPreviews()
+  }
+
   return {
     // Getters
     getNodeOutputs,
@@ -346,6 +359,8 @@ export const useNodeOutputStore = defineStore('nodeOutput', () => {
     revokeAllPreviews,
     revokeSubgraphPreviews,
     removeNodeOutputs,
+    restoreOutputs,
+    resetAllOutputsAndPreviews,
 
     // State
     nodeOutputs,