Diff editor: no horizontal scrollbar after turning word wrap off, so the hidden text cannot be reached

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version: 1.134.0 (110a328ea54b42367b803ec53ee0bf52ef26b419, arm64)
- OS Version: macOS 26.5 (Darwin 25.5.0), arm64

Steps to Reproduce:

1. Open a diff of a file that has lines wider than the editor. Any language reproduces it.
2. Press `Alt+Z` (`Option+Z` on macOS), or run **View: Toggle Word Wrap**, to turn word wrap off.

## Actual

Long lines are cut off at the right edge. No horizontal scrollbar appears where one is expected, and horizontal scrolling with the wheel or the trackpad does nothing. The hidden text cannot be reached at all. Turning word wrap back on is the only way to read it.

A Markdown diff with word wrap on. The lines wrap onto continuation rows, which leaves the table unreadable because the pipes no longer line up:

The same diff with word wrap off. The lines are cut off at the right edge, and no horizontal scrollbar appears between the last line and the status bar:

The same pair on a Dart file, word wrap on then off:

## Expected

A horizontal scrollbar, as in a normal editor.

## Notes

- Reproduced on Markdown and on Dart, so it does not look specific to one language.
- Markdown is where it hurts most. Markdown diffs are wrapped by default, and wrapping makes tables unreadable because the pipes no longer line up. Turning wrapping off to get them readable hides part of the content instead, so neither state allows reviewing the diff.
- I have no custom word wrap or scrollbar settings.