Generalise the palette so Enter advances any pref to its next value and
wraps; a boolean toggle is the two-option case. Both string prefs share a
next_option(current, &OPTIONS) helper (off-list values snap to the head).
- theme (light/dark): rendered as a single whole-frame Frame::invert at the
end of draw(), so text, selection, caret, panel and palette flip together.
- auto_sync: cycles 2m/5m/10m/15m/30m. Set-ahead only — still read by
nothing until the v0.7 periodic push.
toggle_pref -> cycle_pref; palette hint "Enter toggle" -> "Enter change".
f37da21462