Caret stays in correct position when deleting next to non-editable in Firefox

현상

In Firefox, when deleting the last character before a non-editable element in a contenteditable div, the caret correctly stays adjacent to the remaining content instead of jumping to the end.

재현 예시

1. Focus on contenteditable element.
2. Text contains non-editable element (e.g., “Hello @user again”).
3. Delete character just before the non-editable element (Backspace or Delete key).

관찰된 동작

• Correct behavior: Caret stays adjacent to the non-editable element
• No jumping: Caret doesn’t jump to end of editor
• User can continue typing: Can immediately type next character
• Works correctly: Firefox handles deletion properly

참고사항

This is a control case demonstrating that the issue is Chrome-specific and Firefox works correctly.