Investigate transition suppression for nested `data-mode`

Based on changes in #220, `data-mode` could be applied to any container, not just the document root. However, the `ThemeProvider` transition suppression currently only watches `document.documentElement`.

This works for our current Storybook use case, where nested themes are static, but it may not be sufficient if we later support components that switch between light and dark mode independently (for example, code editors or previews).

**Task**

- Review whether transition suppression should also support nested `data-mode` containers.
- Decide whether the current behaviour is sufficient or should be extended.

Comienza revisando el comportamiento de supresión de transiciones de ThemeProvider y los cambios del issue #220, centrándote en cómo se observa actualmente document.documentElement. Compara ese comportamiento con contenedores data-mode anidados y documenta si el comportamiento actual es suficiente o define el alcance necesario para admitir el cambio independiente de temas anidados.

Escrito por el modelo de indexación a partir del texto del issue.