Four-level build grading and copyable examples

What changed

• Build grading rates each requirement as Missing, Below, Meets, or Exceeds expectations, instead of met or not met.
• When copying a No AI question is blocked, code examples and sample inputs now stay copyable. The block is off unless the organizer turns it on.
• When a whole room starts at once, everyone gets a Machine, even when starts have to wait and retry.