Function reset_arena_keyed_reports 

pub fn reset_arena_keyed_reports()

Clear the arena-SymStr-keyed report maps (undefined, missing). MUST be called whenever the arena is reset (see crate::reset_thread_engine): their keys are arena interner ids, so after arena::reset() a stale key resolves to whatever string now occupies that id — e.g. a \special_relax family-token name — producing phantom “undefined macro” reports across conversions.