Codex Diff missing background highlights on Remote-SSH

What version of the IDE extension are you using?

26.406.31014

What subscription do you have?

GPT Plus

Which IDE are you using?

VS Code

What platform is your computer?

Darwin 25.4.0 arm64 arm

What issue are you seeing?

In the Codex Diff view over an SSH connection, the red/green background highlights for changed lines are missing.

<img width="1360" height="214" alt="Image" src="https://github.com/user-attachments/assets/316d9aae-f1e4-4c6f-bd3e-e05308a32b7d" />

<img width="1354" height="212" alt="Image" src="https://github.com/user-attachments/assets/db3c25f3-7f9d-45af-851b-5c6209a4f412" />

What steps can reproduce the bug?

1. Open VS Code and connect to a remote server using the Remote-SSH extension.
2. Open a project and modify any file.
3. Trigger a code edit using Codex, which opens the Codex Diff view for review.
4. Observe that the red (deleted) and green (added) line-level background highlights are completely transparent/missing.
5. Attempting to reload the window or change themes does not resolve the issue.

The specific code doesn't matter; all Codex-generated edits consistently fail to render the expected line-level background highlights.

What is the expected behavior?

The Codex Diff view should render full-width background highlights (red for deletions, green for additions).

Additional information

_No response_