cleanLayout's job is to let a layout outlive the columns it names, and it
walked every config field that carries a column name except aggregates --
which carries one as its key and, in the multi-arg form, a second as the
weight. Empty in practice today, so nothing was breaking; the first
explicit aggregate would have made a later column change abort the whole
restore rather than lose one entry.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>