Support widget specific contextmenu options in vue (#8431)

<img width="614" height="485" alt="image"
src="https://github.com/user-attachments/assets/2a635dec-8bed-4fab-9881-5e6057d482e1"
/>

These options were defined in `litegraphService`. While the existing
code for defining options is reused (to ensure there's no implementation
drift) these extra widget options use the litegraph format for context
menu options and do not belong in `useSelectionMenuOptions`. They have
been moved out of `useLitegraphService` (good), but left in
`litegraphService` (not great)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8431-Support-widget-specific-contextmenu-options-in-vue-2f76d73d3650814fb20fca352dc81e3b)
by [Unito](https://www.unito.io)

src/core/graph/subgraph/proxyWidgetUtils.ts

@@ -105,6 +105,7 @@ export function addWidgetPromotionOptions(
       content: `Promote Widget: ${widget.label ?? widget.name}`,
       callback: () => {
         promoteWidget(node, widget, promotableParents)
+        widget.callback?.(widget.value)
       }
     })
   else {
@@ -112,6 +113,7 @@ export function addWidgetPromotionOptions(
       content: `Un-Promote Widget: ${widget.label ?? widget.name}`,
       callback: () => {
         demoteWidget(node, widget, parents)
+        widget.callback?.(widget.value)
       }
     })
   }