Function scale_transform_from_payload 

pub fn scale_transform_from_payload(
    projection: &Option<Vec<Vec<f64>>>,
    center: &Option<Vec<f64>>,
    scale: &Option<Vec<f64>>,
    non_intercept_start: Option<usize>,
    projection_ridge_alpha: Option<f64>,
) -> Result<Option<ScaleDeviationTransform>, String>

Build a ScaleDeviationTransform from saved projection metadata.

Returns Ok(None) only when the payload is completely absent; partial payloads are invalid because prediction cannot replay the fitted scale reparameterization unambiguously.