{"ok":true,"free":true,"charged_usd":0,"method":"POST","endpoint":"/v1/delta-witness/preview","example":{"before":{"status":"open","price":10},"after":{"status":"closed","price":12},"policy":{"blocked_paths":["/price"],"required_changed_paths":["/status"]}},"paid_endpoint":"/v1/delta-policy-gate","paid_price_usd":0.03,"note":"Free preview shows caller-provided state hashes and change count. Paid route evaluates all declared policy constraints; neither independently attests origin."}