Function cleanup_node_names 

pub fn cleanup_node_names(cpg: &mut CodePropertyGraph)

Walks all graph nodes and replaces USR‑encoded names with their human‑readable equivalents.

Both the name field (the primary display name) and, for functions and classes, the usr field are cleaned. A usr value starting with "c:" is considered a raw USR and is converted; other values (e.g. file paths) are left unchanged.