Function mdl_cost 

pub fn mdl_cost(grammar: &Grammar, examples: &[String]) -> Mdl

Computes deterministic two-part MDL for grammar on examples.

The total matches the D1 super::eval::mdl encoding: L(G) is the public grammar symbol count multiplied by a deterministic alphabet code width, and L(D | G) charges accepted examples by emitted Unicode scalars plus a stop bit while rejected examples use a UTF-8 escape penalty.