Catppuccin, Gruvbox, Solarized and High contrast themes

Each in light and dark. The published palettes missed AA in 19 places,
mostly Solarized and Catppuccin Latte, so each failing colour is moved
the least distance, toward black or white, that clears every pair it is
drawn in. Solarized dark's base0 had to rise to base1 to read on base02,
so its dim sits between base2 and base1 to keep three steps of type.

tests/contrast.js checks every palette against the pairs the page draws,
and a border that matches the ground it sits on. Its first run caught
Classic's links at 3.7:1 on the source list and Modern's faint at 4.3:1
on inputs; both are tuned. A failed toast moves to --panel, since the
error colours are tuned for the page's grounds, not --raise.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/theme.ts

@@ -13,6 +13,10 @@ const THEMES: Record<string, {name: string, modes: boolean}> = {
   flatremix: {name: 'Flat Remix', modes: true},
   paper: {name: 'Paper', modes: false},
   nordic: {name: 'Nordic', modes: true},
+  catppuccin: {name: 'Catppuccin', modes: true},
+  gruvbox: {name: 'Gruvbox', modes: true},
+  solarized: {name: 'Solarized', modes: true},
+  contrast: {name: 'High contrast', modes: true},
 };
 const MODES: Record<string, string> = {auto: 'Auto (matches your system)', light: 'Light', dark: 'Dark'};
 // Before themes came in light and dark, ipx.theme in localStorage held one of these.