V3 deterministic JSON validation and fixed-query capability pack. By-value connector composition (service_kind=cli, no separate ingredient): the local jq CLI exposes readiness, JSON validation, pretty formatting, top-level key extraction, sorted key listing, document length, and object key-existence checks. This pack deliberately does not expose arbitrary jq filters, module loading, raw input, slurp mode, file/program filters, library paths, or environment overrides. json.validate materializes a file_ref and captures no stdout/stderr; value-returning operations are path-based because requested JSON content or metadata is returned on stdout. Requires jq on PATH (Debian/Ubuntu: apt install jq; macOS: brew install jq). Local and no-egress.