editor: Fix `Open File` from multibuffer header jumping to wrong excerpt (#54652)

Reconciles `Open File` behaviour to the same action as using the
keybinds.

Closes #54502

Release Notes:

- Fixed a bug where the `Open File` button would not jump to the excerpt
containing the active cursor.
6f84d9be2cNeel committed on 4/23/2026, 4:42:38 PM· committed by GitHubparent4733ae4
2 files changedLine totals unavailable