A11y: When tab selection is in Load/Save modal "Or browse a file" shift-tab goes to editor

When tab navigation is used and this link is focused:

Pressing `shit+tab` focuses on the Ace editor behind the modal.

Reproduce the issue in the Load/Save modal by focusing “Or browse a file” and pressing Shift+Tab, then inspect the modal's focus handling. Done means reverse tabbing keeps focus within the modal instead of moving to the Ace editor behind it.

由索引模型根据 Issue 内容生成。