Both themes used bg_terminal, on the assumption the name meant "the
terminal's background". It does not -- the shared Theme struct documents
it as "For terminal output blocks (currently unused, using bg_dark
instead)". The surface grok actually paints is bg_base, so GrokDay was
rendering brighter than grok itself (#f5f5f5 vs #eeeeee) and GrokNight
darker (#0a0a0a vs #141414).
GrokDay's color15 moves from bg_storm to bg (#f5f5f5): bg_storm is now
the background, so bright white would have been invisible against it.
Audited every slot in both files against the source palettes: each value
maps to a named palette color, no text color is under 3:1 on its
background, and cursor and selection overlays clear 4.5:1.
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