Fetch a single live listing by its id or slug, including base_url, price range, network and verification state. Also returns a reliability object: score (0 to 100 or null), band (strong, established, thin, caution or unscored) and computed_at. Reliability is a running score from paid verifications, health history and payTo integrity, not a star rating and not a guarantee; unscored means it has not been computed for that listing yet. Method: https://payapi.market/how-an-agent-finds-payapi. Returns the listing whether or not it is verified, and reports payment_verified honestly. Free and read-only; spends nothing.