Convert between YAML and JSON in one call. to:"json" parses a YAML document (config files, docker-compose, Kubernetes manifests, CI pipelines) into a plain JSON value; to:"yaml" renders any JSON value as clean block-style YAML. Hardened: safe core schema (tags like !!js/function never execute), alias bombs rejected, one document per call, parse errors return line/column. YAML input up to 2 MB UTF-8.