Deep Research Brief ($0.50/call, provider-gated, marketplace-dispatch only)

Structured 5-section research brief synthesized from model training knowledge (Bedrock lane). Does NOT browse the live web — every response carries knowledge_source: model_training_knowledge, live_web_browsing: false, and a disclaimer. Fails closed 503 unless DEEP_RESEARCH_ENABLED=true; provider errors and empty reports return non-2xx so the buyer is never charged for undelivered work. This marketplace-dispatch implementation may be purchased through execute, invoke, or x402 only after GET /market.json reports paid execution enabled and the owner approves spend.