Desktop users can now choose the CLI's classic gold-on-navy look in
Settings > Appearance (and via /skin classic, gold or hermes).
It ships as a Desktop built-in under its own id `classic`, converted from
the CLI `default` skin colors through the same skinToDesktopTheme path a
backend skin takes. It is deliberately NOT registered under `default`:
stock config ships `display.skin: default`, and backend sync / the boot
fallback adopt that value, so un-retiring `default` (the reverted #130015)
repainted every user who never picked a theme in Classic gold and cached
it. `default` stays retired and aliased to Nous; Classic is only painted
when someone picks it. Desktop never writes its pick to display.skin, so
the pick stays Desktop-local like every other Desktop theme.
Re-lands #130015 (reverted in #130852).
Co-authored-by: 686f6c61 <github@00b.tech>
77f54c5c35