[feat] Add context menu converter infrastructure (#7113)

## Summary
- Add `contextMenuConverter.ts` with utilities for converting LiteGraph
context menu items to Vue menu format
- Improve `contextMenuCompat.ts` with set-based diffing for more
reliable legacy extension detection
- Extend `MenuOption`/`SubMenuOption` types with `source`, `disabled`,
`isColorPicker`, and `category` type fields
- Add unit tests for converter functions

## Context
This is foundational work for migrating the node context menu from a
custom Popover-based component to PrimeVue ContextMenu.

The converter provides:
- Menu ordering and section grouping (core items first, then extensions)
- Deduplication with preference for Vue-native items over LiteGraph
items
- Extension categorization with labeled section
- Support for disabled states and color picker submenus

## Test plan
- [x] Unit tests pass for `buildStructuredMenu` (9 tests)
- [x] Unit tests pass for `convertContextMenuToOptions` (7 tests)
- [x] Typecheck passes
- [x] Lint passes
- [x] Knip passes (no unused exports)

## Related
This is PR 1 of 2 for the node context menu migration. PR 2 will wire up
the UI component.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7113-feat-Add-context-menu-converter-infrastructure-2be6d73d3650816ca6c9d2cf50f10159)
by [Unito](https://www.unito.io)

src/composables/useContextMenuTranslation.ts

@@ -22,7 +22,10 @@ export const useContextMenuTranslation = () => {
     this: LGraphCanvas,
     ...args: Parameters<typeof getCanvasMenuOptions>
   ) {
-    const res: IContextMenuValue[] = getCanvasMenuOptions.apply(this, args)
+    const res: (IContextMenuValue | null)[] = getCanvasMenuOptions.apply(
+      this,
+      args
+    )
 
     // Add items from new extension API
     const newApiItems = app.collectCanvasMenuItems(this)
@@ -58,13 +61,16 @@ export const useContextMenuTranslation = () => {
     LGraphCanvas.prototype
   )
 
+  // Install compatibility layer for getNodeMenuOptions
+  legacyMenuCompat.install(LGraphCanvas.prototype, 'getNodeMenuOptions')
+
   // Wrap getNodeMenuOptions to add new API items
   const nodeMenuFn = LGraphCanvas.prototype.getNodeMenuOptions
   const getNodeMenuOptionsWithExtensions = function (
     this: LGraphCanvas,
     ...args: Parameters<typeof nodeMenuFn>
   ) {
-    const res = nodeMenuFn.apply(this, args)
+    const res = nodeMenuFn.apply(this, args) as (IContextMenuValue | null)[]
 
     // Add items from new extension API
     const node = args[0]
@@ -73,11 +79,28 @@ export const useContextMenuTranslation = () => {
       res.push(item)
     }
 
+    // Add legacy monkey-patched items
+    const legacyItems = legacyMenuCompat.extractLegacyItems(
+      'getNodeMenuOptions',
+      this,
+      ...args
+    )
+    for (const item of legacyItems) {
+      res.push(item)
+    }
+
     return res
   }
 
   LGraphCanvas.prototype.getNodeMenuOptions = getNodeMenuOptionsWithExtensions
 
+  legacyMenuCompat.registerWrapper(
+    'getNodeMenuOptions',
+    getNodeMenuOptionsWithExtensions,
+    nodeMenuFn,
+    LGraphCanvas.prototype
+  )
+
   function translateMenus(
     values: readonly (IContextMenuValue | string | null)[] | undefined,
     options: IContextMenuOptions