Constant PIO_PAYLOAD_BALANCED_SCHEMA_URL 

pub const PIO_PAYLOAD_BALANCED_SCHEMA_URL: &str = "https://powerio.dev/schema/pio-payload-balanced/1";

The declared schema URL for the balanced payload (model.balanced_network).

Payload schema URLs are identifiers, not fetch locations (the same convention as JSON Schema $id). The payload contract they name is the serde snapshot documented in docs/src/pio-json-schema.md.