Function name_taken 

fn name_taken(defs: &[AgentDefinition], name: &str) -> bool

Whether a user agent (not a seeded template) already goes by name, case-insensitively: as its name, or as its branch label, which is what a renamed fork shows. Names are unique among user agents: the picker lists them by name, and name-keyed registrations collide otherwise. A launched agent’s instance name is the store’s to check (agents_matching_name).