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>

CHANGELOG.md

@@ -7,6 +7,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Four themes, each in light and dark: Catppuccin (Latte and Mocha), Gruvbox, Solarized, and High
+  contrast, black and white with every colour at 7:1 or more.
+
+### Fixed
+
+- Links in Classic, and hints and headings in Modern's dark half, are dark or light enough to
+  read comfortably. A failed-action message is easier to read in every theme.
+
 ## [0.8.1] - 2026-09-19
 
 ### Changed