AdaptiveWidget

Renders kvadrant on a Metro surface and material anywhere else.

On the model compose-cupertino proved — the only working precedent for a second design language beside Material in a Kotlin Multiplatform project (research §1.1). The decision is KvadrantTheme.present, which is false unless a theme actually provided it, rather than any of the theme's values: every other local here has a working default, so reading one says nothing about whether anybody is above you.

It is a demonstration more than a tool. A component library cannot know which of two design languages a screen wants, and a caller who does know can simply write the if — what this earns its place on is making "drop Metro into your existing application" a thing somebody can try in one line before committing to it.