Submitted work opens as one workspace

What changed

• In candidate review, Overview now shows the submitted work as one workspace, with a tab for each question and the same Preview and Code buttons the candidate used.
• A View replay button plays the session from the start, and the replay's problem panel can be resized the way the candidate's could.
• On wide screens the candidate table fits without a sideways scrollbar. The Assessment Copilot composer says when Enter will queue a message while a reply is still running.