tabindex attribute does not control focus order correctly

Phenomenon

When multiple contenteditable regions have tabindex attributes, the tab order may not follow the tabindex values correctly in Edge. The focus order may be inconsistent or incorrect.

Reproduction example

1. Create multiple contenteditable divs with different tabindex values:

   <div contenteditable tabindex="3">Third</div>
   <div contenteditable tabindex="1">First</div>
   <div contenteditable tabindex="2">Second</div>

2. Use Tab key to navigate.
3. Observe the focus order.

Observed behavior

• In Edge on Windows, tabindex may not control focus order correctly.
• The focus may skip elements or follow an unexpected order.
• Keyboard navigation is inconsistent.

Expected behavior

• tabindex should control focus order as specified.
• Elements should be focused in the order of their tabindex values.
• Keyboard navigation should be predictable and accessible.