The field comment claimed the cli layer replaces the UI writer with a
discarding writer in --cron mode. It does not: the writer is created
once as ui.New(os.Stdout) and never reassigned, and setupGlobals calls
UI.SetQuiet(true) instead. Quiet mode drops Begin, Complete, Info,
Notice, Detail, Progress, and Banner, but Warningf and Errorf have no
quiet check and always emit, so --cron does not make the writer silent.
The README's --cron bullet had the adjacent understatement ("Silent
unless error"), and now names warnings as well.
Comments and documentation only; no behavior change.
