Follow OS color scheme by default, with a three-way toggle
(System / Light / Dark) in the kebab menu. Light theme uses warm,
neutral tones with soft card-to-background contrast. Semantic colors
(damage, healing, conditions) keep their hue across themes.
Closes#10
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
