Function register_reason_flag 

pub fn register_reason_flag(command: Command) -> Command

Registers the --reason flag on a clap command.

Not part of register_global_flags: --reason is only meaningful when an app has registered an Authorizer, Auditor, or ActivityEmitter to consume it (see Cli::new’s conditional call to this function). Apps with none of those configured never register this flag at all, rather than exposing a flag that nothing reads. Cli::new only checks the eager authz/auditor/ activity fields on CliConfig; installing one of these later via init_deps does not register --reason, since flag registration happens before init_deps runs.