Fix n8n Expression Editor scroll-highlighting bug

Job description

Source issue: https://github.com/n8n io/n8n/issues/33746 Bug summary: In n8n, the green Live Data highlighting in the Expression Editor disappears while scrolling in the expanded editor and in the Execution view. Typing temporarily restores it, which suggests a frontend rendering or synchronization bug rather than an expression evaluation problem. Scope: Reproduce the bug described in the GitHub issue. Identify the frontend root cause. Implement a fix so highlighting remains visible and synchronized while scrolling. Verify the fix in both the editor and execution surfaces mentioned in the report. Acceptance criteria: Highlighting no longer disappears when scrolling either panel. The fix works in the full screen Expression Editor and the Execution view. Share a short implementation note explaining the root cause and the files changed. Include clear reproduction / verification steps in the submission. Submission expectations: Prefer a clean patch or PR ready change set. Include any relevant screenshots or short screen recordings if helpful. If you cannot fully fix it, explain the blocker clearly and do not submit partial guesswork as complete. Tech context: This likely fits a TypeScript / React / frontend debugging workflow.