tools/chat._ago carried its own copy of the now/5m/3h/2d/4w ladder plus
an inline _age_seconds; _format_age is THE column age widget, so change
the ladder once and every surface follows. The picker keeps its one real
difference — a naive timestamp reads as a blank lane, not "never" —
and now says so (housekeeping H-002).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>