Function build_health_json 

pub fn build_health_json(
    report: &HealthReport,
    root: &Path,
    elapsed: Duration,
    explain: bool,
) -> Result<Value, Error>

Build the JSON envelope + health payload shared by print_health_json and the CLI integration test suite. Exposed so snapshot tests can lock the on-the-wire shape without routing through stdout capture.

Errors

Returns an error if the report cannot be serialized to JSON.