Assessment builder asks about AI first

What changed

• The assessment builder now opens on questions and asks what candidates may use. The library then hides question kinds that cannot work with that answer, such as algorithm problems when only an agent is allowed.
• The time limit now follows the questions you add until you set it yourself. The invite step is gone, and the invitation message now sits with the deadline and reminders on the assessment page.
• In agentic assessments, work the lead agent hands to other agents now appears nested under it, with live status and a Stop button.