A dark/light theme toggle.
<.theme_toggle />The SkuaTheme hook flips data-theme on <html> between dark and
light, persists the choice to localStorage, and applies it on mount.
Skua ships dark-first; the light token set lives in assets/css/skua.css
under :root[data-theme="light"], so toggling re-skins every component with
no per-component work.
To avoid a flash of the wrong theme on first paint, the installer also adds a tiny pre-paint script to the root layout; without it the toggle still works, it just settles a frame after load.