Stabilize MarkEditMac context-menu tests

[Copilot]

The MarkEditMac job failed in context-menu tests because the menu could still be opening when the test helper’s one-shot check ran.

• Change: Poll during menu tracking and assert the highlight once the menu is presented.

Checklist

• I have followed the development guide and matched the existing code style
• I have performed a self-review of my own code, kept the diff minimal, and avoided unrelated changes
• I have smoke tested the change, covering the main affected paths
• For user-visible strings: localization keys have been added/updated as needed
• For UI changes: I have attached before/after screenshots or a short screen recording

[cyanzhong]

@copilot Test still fails, try understand this better.

[Copilot]

@copilot Test still fails, try understand this better.

The logs show both ContextMenuTests passed; the job failed afterward because those tests only ordered out their NSPanel instances, leaving them in NSApp.windows and failing EditorDocumentTests.setUp(). I changed both teardowns to close the panels and reverted the unrelated polling change in b53c62a.