add save option for 3d node on context menu (#6319)

## Summary

add save option for 3d node on context menu

## Changes
allow to export model from context menu, supported in
preview3d/load3d/saveMesh




https://github.com/user-attachments/assets/1f0f1a93-9cdb-477f-8bd3-e298c7e3892b

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6319-add-save-option-for-3d-node-on-context-menu-2996d73d365081f7853cd2ae9c69fe4d)
by [Unito](https://www.unito.io)

src/extensions/core/saveMesh.ts

@@ -1,6 +1,7 @@
 import { nextTick } from 'vue'
 
 import Load3D from '@/components/load3d/Load3D.vue'
+import { createExportMenuOptions } from '@/extensions/core/load3d/exportMenuHelper'
 import Load3DConfiguration from '@/extensions/core/load3d/Load3DConfiguration'
 import { type CustomInputSpec } from '@/schemas/nodeDef/nodeDefSchemaV2'
 import { ComponentWidgetImpl, addWidget } from '@/scripts/domWidget'
@@ -60,6 +61,10 @@ useExtensionService().registerExtension({
 
       const load3d = useLoad3dService().getLoad3d(node)
 
+      if (load3d) {
+        node.getExtraMenuOptions = createExportMenuOptions(load3d)
+      }
+
       const modelWidget = node.widgets?.find((w) => w.name === 'image')
 
       if (load3d && modelWidget) {