[feat] Replace NodeOptions with PrimeVue ContextMenu (#7114)

## Summary
- Add `NodeContextMenu.vue` using PrimeVue ContextMenu component with
native submenu support
- Rename `SubmenuPopover.vue` to `ColorPickerMenu.vue` (specialized for
color picker)
- Delete old components: `NodeOptions.vue`, `MenuOptionItem.vue`,
`useSubmenuPositioning.ts`
- Wire up context menu converter in `useMoreOptionsMenu.ts`
- Update tests to use hover instead of click for submenus

## Dependencies
**This PR depends on #7113** - the context menu converter infrastructure
PR. It should be merged after that PR.

## Benefits
- Native PrimeVue submenu support with proper keyboard navigation
- Constrained menu dimensions with overflow scrolling (max-h-[80vh])
- Cleaner component architecture with ~280 fewer lines of code
- Better separation: ColorPickerMenu handles only the custom color
picker UI

## Test plan
- [x] Typecheck passes
- [x] Lint passes
- [x] Knip passes
- [ ] Browser tests for submenu interactions pass
- [ ] Manual testing of node context menu

## Screenshots
(Menu UI should look the same, with improved submenu behavior)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7114-feat-Replace-NodeOptions-with-PrimeVue-ContextMenu-2be6d73d365081fda576fd691175eacf)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

src/composables/canvas/useSelectionToolboxPosition.ts

@@ -21,10 +21,10 @@ import { computeUnionBounds } from '@/utils/mathUtil'
  */
 
 // Shared signals for auxiliary UI (e.g., MoreOptions) to coordinate hide/restore
-export const moreOptionsOpen = ref(false)
-export const forceCloseMoreOptionsSignal = ref(0)
-export const restoreMoreOptionsSignal = ref(0)
-export const moreOptionsRestorePending = ref(false)
+const moreOptionsOpen = ref(false)
+const forceCloseMoreOptionsSignal = ref(0)
+const restoreMoreOptionsSignal = ref(0)
+const moreOptionsRestorePending = ref(false)
 let moreOptionsWasOpenBeforeDrag = false
 let moreOptionsSelectionSignature: string | null = null