- Collapse the 10 theme cards into 5 pairs: light swatches top row, dark bottom row
- Dark mode toggle in settings and topbar (sun/moon inline SVG)
- Toggling dark mode switches to the other variant of the selected pair
- Persist pair id in localStorage palette-theme, dark flag in palette-dark
- Head script resolves base+dark to variant; URL ?theme= accepts both ids and wins
- Settings gear highlights like nav tabs on /settings
- PALETTE_DEFAULT_DARK env var sets server default dark state (default on)
- Server-side resolution helpers + tests
