Axismundi Theme Switcher

The axismundi/theme-switcher block puts an Auto / Light / Dark control on the
page, as a connected button group or a single cycling button, and writes the
choice to html[data-theme]. The choice is kept in a first-party cookie and
reapplied before the next page paints, so returning to the site does not flash
the wrong scheme.

The block reads its colors, corner sizes and motion from the Material Design
system custom properties, so it looks as intended under any theme that publishes
them, and falls back to Material’s own baseline where a theme publishes none.
The Axismundi theme supports the html[data-theme] contract natively.