Weird behaviour of cursor and focus with images

What’s broken?

Focus on image
Arrow up and the cursor goes above but not on a line if no line is actually above.
Or arrow down but nothing happens. It doesn't go to the empty line bellow.
To create the empty line I have to click below the image with my mouse

What did you expect to happen?

if no element above the image, with arrow up, focus should stay on image
With arrow down it should create an empty line for the cursor to move down and save a click

Steps to reproduce

https://github.com/user-attachments/assets/fb21d53e-c130-4083-a990-e8815a107698

BlockNote version

https://www.blocknotejs.org/demo#7ixm8

Environment

No response

Additional context

No response

Contribution

• I'd be interested in contributing a fix for this issue

Sponsor

• I'm a sponsor and would appreciate if you could look into this sooner than later 💖

Reproduce the image cursor and focus behavior from the linked video and BlockNote demo, then trace the editor's image-selection and arrow-key handling. Done means Arrow Up keeps focus on the image when there is no element above, while Arrow Down creates or reaches an empty line below without requiring a mouse click.