Accessible diff viewer up/down focuses out of accessible diff view

[anthonykim1]

Normally, with the accessible diff viewer, pressing arrow key down will move the focus inside the accessible diff view, but focus on the lines below.

There is a bug where the focus rather moves to different cell rather than inside the accessible diff view, leaving screen reader user confused.

Note: Screen reader optimized mode is enabled to repro the issue.

Python file (correct behavior where focus moves inside accessible diff viewer):

Screen.Recording.2025-06-09.at.12.58.40.PM.mov

Notebook (focus moves to different cell)
https://github.com/user-attachments/assets/6904cd4f-2588-4165-85fa-1caca86e9ec6

/cc @meganrogge @jooyoungseo

[amunger]

The only solution I can think of is creating a new context key for a11y diff view focused, and adding that to the when clause.

• While in the accessible diff view, the cell list view still has focus, so we run the commands list.focusup and list.focusdown.
• The diff view is just a monoco component that does not use commands to move up and down the rows.
• current list.focusDown when clause is listFocus && !inputFocus && !treestickyScrollFocused
• There doesn't seem to be any context key for being focused in the diff view.

@joaomoreno, @meganrogge - Does that seem reasonable?