Add UI code for configuring subgraphNode widgets (#5826)

The third PR for managing display of widgets on subgraph nodes. This is
the one that actually makes the functionality usable and user visible.

Adds
- A right-side modal for configuring which widgets are promoted,
accessed by right click or selection toolbar
- This menu allows for re-arranging widget order by dragging and
dropping.
- Indicators inside the subgraph for which widgets have been promoted.
- Context menu options for promoting or demoting widget inside of a
subgraph.
<img width="767" height="694" alt="image"
src="https://github.com/user-attachments/assets/4f78645d-7b26-48ba-8c49-78f4807e89e8"
/>
<img width="784" height="435" alt="image"
src="https://github.com/user-attachments/assets/7005c730-a732-481e-befb-57019a8a31a7"
/>


Known issues
- Some preview widgets are not added to a node until a draw operation
occurs. The code does not yet have a way of determining which nodes
should have draw operations forced to facilitate initial widget
creation.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5826-Add-UI-code-for-configuring-subgraphNode-widgets-27c6d73d36508146accbf395e5bcd36a)
by [Unito](https://www.unito.io)

src/scripts/app.ts

@@ -5,6 +5,7 @@ import { reactive, unref } from 'vue'
 import { shallowRef } from 'vue'
 
 import { useCanvasPositionConversion } from '@/composables/element/useCanvasPositionConversion'
+import { registerProxyWidgets } from '@/core/graph/subgraph/proxyWidget'
 import { st, t } from '@/i18n'
 import {
   LGraph,
@@ -883,6 +884,7 @@ export class ComfyApp {
         }
       }
     )
+    registerProxyWidgets(this.canvas)
 
     this.graph.start()