Idempotent seeder inserts public, unowned demo scenarios from backend/app/seed_data/*.json if a public scenario with the same title is missing, so a fresh Neon database (and any clone) gets demo content guests can play immediately. Ships two scenarios: the Sunken Crypt of Vharos (all four script hooks) and Signal from the Derelict (sci-fi, context-engine focused). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TEpWMjnfPqzZ13nPMoGhs5