Function resolve_alias 

pub fn resolve_alias(model: &str, extra: &[(&str, &str)]) -> String

Expand a friendly model alias to its full slug, consulting extra (config-provided aliases, §3.1 capabilities.model_catalog.aliases) BEFORE DEFAULT_ALIASES — a config-provided alias may override a built-in one (e.g. re-pointing "opus" at a different slug), but an unknown value always passes through unchanged so any real slug still works. extra is typically empty (no config wired it in), in which case this is exactly the CLI’s original resolve_model_alias behavior.