Initialize the theme switch button cycle and system preference listener.
Sync the <meta name="theme-color"> tag with the current color scheme.
Apply a theme mode and emit the fixit:switch-theme event.
'auto', 'light', or 'dark'.
Whether to save the choice to localStorage (default: true).
Initialize theme color and switch handler.
Theme module — color scheme switching and theme-color meta tag management.
Responsibilities:
<meta name="theme-color">based on current scheme.