Function lower_multiconductor_to_balanced 

pub fn lower_multiconductor_to_balanced(
    net: &MulticonductorNetwork,
    options: MulticonductorToBalancedOptions,
) -> Result<MulticonductorToBalancedLowering, MulticonductorToBalancedError>

Lower a transparent three phase multiconductor network to a balanced model.

The pass is explicit. It does not run from readers, writers, matrix builders, bindings, or package deserialization. Unsupported inputs return structured LOWER.MULTI_TO_BALANCED.* diagnostics in MulticonductorToBalancedError.