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/core/schemas/proxyWidget.ts

@@ -4,18 +4,12 @@ import { fromZodError } from 'zod-validation-error'
 import type { NodeProperty } from '@/lib/litegraph/src/LGraphNode'
 
 const proxyWidgetsPropertySchema = z.array(z.tuple([z.string(), z.string()]))
-type ProxyWidgetsProperty = z.infer<typeof proxyWidgetsPropertySchema>
+export type ProxyWidgetsProperty = z.infer<typeof proxyWidgetsPropertySchema>
 
 export function parseProxyWidgets(
   property: NodeProperty | undefined
 ): ProxyWidgetsProperty {
-  if (typeof property !== 'string') {
-    throw new Error(
-      'Invalid assignment for properties.proxyWidgets:\nValue must be a string'
-    )
-  }
-  const parsed = JSON.parse(property)
-  const result = proxyWidgetsPropertySchema.safeParse(parsed)
+  const result = proxyWidgetsPropertySchema.safeParse(property)
   if (result.success) return result.data
 
   const error = fromZodError(result.error)