Premortem Report ($1.50 paid listing implementation)

First-party implementation route for the Premortem Report paid listing. Marketplace-dispatch only: unsigned direct POSTs return marketplace_dispatch_required. Only after GET /market.json reports paid execution enabled and the owner approves spend may external buyers purchase through /api/execute, /api/invoke/{listing_id}, or x402. Runs the pinned premortem engine in an empty scratch directory, is deterministic for identical plans, and fails closed on engine errors.