Lazy list helpers, and what each one gets wrong

Four utilities, each a handful of lines, each with a failure mode that only shows in a real list. Keep them together: they all read layoutInfo — the last completed layout, never the next one.

Scroll direction, as derived state

// adapted: logging removed, list and grid variants collapsed into one
@Composable
fun LazyListState.isScrollingUp(): State<Boolean> {
    var previousIndex by remember(this) { mutableIntStateOf(firstVisibleItemIndex) }
    var previousOffset by remember(this) { mutableIntStateOf(firstVisibleItemScrollOffset) }