Expose dropdown open/close events to allow external scroll locking

Currently, it is not possible to track whether an editor dropdown (e.g. suggestion menu, formatting menu) is open from outside the editor.

This makes it difficult to prevent background scrolling, especially in layouts where the editor is placed inside a custom scrollable container rather than relying on document.body.

Expected Behavior

• A callback or event when an editor dropdown opens or closes
• Allow consumers to:
  • Disable scrolling on their own scrollable container
  • Re-enable scrolling when the dropdown is closed

This would make dropdown interactions easier and more predictable in complex layouts.

Start by locating the editor dropdown implementations, including the suggestion and formatting menus, and review how their open and close state is managed. Then examine existing external callbacks or events before defining an API that lets consumers control scrolling in a custom scrollable container. Done means consumers can detect both dropdown transitions and restore scrolling after closure.