Function load_versioned_ns 

pub fn load_versioned_ns(
    globals: Arc<GlobalEnv>,
    spec: &RequireSpec,
    commit: &str,
    current_ns: &str,
) -> EvalResult<()>

Load spec.ns at commit, registering the result as the namespace "<spec.ns>@<commit>" in the global namespace table.

Idempotent: if the versioned namespace is already loaded, only applies the alias/refer from spec in current_ns. The actual loading lives in crate::env::versioned::ensure_versioned_ns_loaded, shared with the per-symbol resolver used by all execution tiers.