Fix a hydration mismatch in output that starts with a blank line
The HTML parser drops a newline right after <pre>'s opening tag, so check output beginning with one (cargo test -q's does) rendered differently in the browser than on the server. Output now sits in a <code> inside the <pre>, where the newline survives. A client entry logs any future mismatch with the component it happened in.
No changes
This commit changes no files.