Further subgraph improvements (#6466)

- Prune disconnected widgets on config panel open
- Fix breakage of DOMWidgets on double nest
- Fix self clipping of proxied DOMWidget nodes
- Blacklist cloning of promtoed widget prop

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6466-Further-subgraph-improvements-29c6d73d365081c8b63dda068486805c)
by [Unito](https://www.unito.io)

src/core/graph/subgraph/proxyWidget.ts

@@ -48,9 +48,12 @@ type Overlay = Partial<IBaseWidget> & {
  * on the linked widget
  */
 type ProxyWidget = IBaseWidget & { _overlay: Overlay }
-function isProxyWidget(w: IBaseWidget): w is ProxyWidget {
+export function isProxyWidget(w: IBaseWidget): w is ProxyWidget {
   return (w as { _overlay?: Overlay })?._overlay?.isProxyWidget ?? false
 }
+export function isDisconnectedWidget(w: ProxyWidget) {
+  return w instanceof disconnectedWidget.constructor
+}
 
 export function registerProxyWidgets(canvas: LGraphCanvas) {
   //NOTE: canvasStore hasn't been initialized yet
@@ -167,7 +170,7 @@ function resolveLinkedWidget(
   if (!n) return [undefined, undefined]
   const widget = n.widgets?.find((w: IBaseWidget) => w.name === widgetName)
   //Slightly hacky. Force recursive resolution of nested widgets
-  if (widget instanceof disconnectedWidget.constructor && isProxyWidget(widget))
+  if (widget && isProxyWidget(widget) && isDisconnectedWidget(widget))
     widget.computedHeight = 20
   return [n, widget]
 }