ISSUE-018 — Active-retrieval nudge vs generic reminder experiment

[shivaram19]

• Functional surgeon view: Telegram users are randomly assigned to either a generic reminder or an active-retrieval quiz nudge; quiz-start rate is measured.
• Acceptance criteria:
  1. Random assignment at consent time.
  2. Nudge message contains one question and a reply path.
  3. quiz_started event attributed to treatment arm.
• Dependencies: ISSUE-017 (Telegram scaffold), ISSUE-003 (content bank ≥100 for meaningful sample).