MATE's Appearance dialog skips any metatheme without IconTheme
(mate-control-center capplets/common/mate-theme-info.c), so Diehard4 was
applied but never listed: it showed as Custom, and switching away lost it.
menta and mate-black are MATE's defaults, so selecting the theme leaves
icons and cursor as they were.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
