Function lower_model 

pub fn lower_model(
    file: &str,
    model: &ModelDecl,
) -> Result<CompiledModel, Vec<Diagnostic>>

Resolve and lower one parsed model declaration.

Graph IDs are fresh in v0. Persistent source-anchor identity is deliberately a later incremental-compiler contract rather than a hash hidden here.

Errors

Returns source-spanned name, dimension, clock, connection, or DAG diagnostics. No partial transaction is returned.