AdaptiveNavScaffold
fun <T> AdaptiveNavScaffold(items: List<TabBarItemData<T>>, selection: T, onSelectionChange: (T) -> Unit, modifier: Modifier = Modifier, topBar: @Composable () -> Unit = {}, colors: TabBarItemColors = TabBarDefaults.itemColors(), scrollBehavior: TabBarScrollBehavior? = null, content: @Composable (PaddingValues) -> Unit)
A scaffold that shows a TabBar in compact windows (narrower than 600 dp) and a NavRail in wider ones, with topBar above the content. scrollBehavior only applies to the tab bar; the rail stays put.