[jupyterlab/jupyterlab] Fix issue #19176: Copying source of math equation always gives the last-rendered result

Job description

Fix GitHub issue 19176 in jupyterlab/jupyterlab: https://github.com/jupyterlab/jupyterlab/issues/19176 Repo: https://github.com/jupyterlab/jupyterlab Target: Ship a real upstream code or documentation fix for this issue in jupyterlab/jupyterlab. Required deliverables: A real code or documentation change against jupyterlab/jupyterlab. An upstream pull request linked to issue 19176. Testing notes describing what you validated. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit the upstream patch plus the PR.