Reorder drag has no visible affordance on dark backgrounds: dragging flag is spent on an invisible shadow

Summary

List computes whether a row is being dragged and spends it entirely on
Modifier.shadow(8.dp). On a dark app that shadow is invisible, so a reorder has
no visible affordance at all — the row you are dragging looks identical to
every other row. There is no way to reach the flag from Swift to supply your own
treatment.

Where

Sources/SkipUI/SkipUI/Containers/List.swift, RenderReorderableItem:

@Composable private func RenderReorderableItem(reorderableState: ReorderableLazyListState, key: String, modifier: Modifier, content: @Composable (Modifier) -> Void) {
    ReorderableItem(state: reorderableState, key: key, defaultDraggingModifier: modifier) { dragging in
        var itemModifier = Modifier.detectReorderAfterLongPress(reorderableState)
        if dragging {
            let elevation = animateDpAsState(8.dp)
            itemModifier = itemModifier.shadow(elevation.value)
        }
        content(itemModifier)
    }
}

dragging is known here and discarded. A shadow communicates elevation by
darkening what is around the row, which does nothing over #000/#141414.
Material's own answer on dark surfaces is tonal elevation — the surface gets
lighter — which a shadow cannot express.

Why an app cannot work around it

• The flag never reaches Swift. onMove is invoked from onDragEnd
  (rememberReorderableLazyListState(..., onDragEnd:) → commitMove()), so
  SwiftUI's .onMove fires on drop. During the drag the app knows nothing.
• A gesture of one's own does not fire. Modifier.detectReorderAfterLongPress
  claims the long press first, so .onLongPressGesture(..., onPressingChanged:)
  on the row never sees the press. Verified on device.
• And that callback is one-way regardless. onLongPressChange() calls
  onChanged(true); nothing ever calls it with false
  (System/Gesture.swift), so a press-derived highlight would latch on rather
  than follow the finger.

Suggested directions

1. Apply a tonal treatment as well as the shadow when dragging — e.g. compose the
   row over a surface tinted by elevation, so dark themes get feedback that a
   shadow cannot give them.
2. Or make it configurable, in the shape material3Ripple already uses: an
   environment hook letting the app supply the dragging modifier.
3. Or expose dragging to the row content so the app can style it, which is what
   SwiftUI apps do on iOS anyway.

Any one of these turns a currently-invisible interaction into a visible one. (1)
alone would fix it for every dark-themed Skip app without an API change.

Environment

skip-ui as vendored in a Skip app, Android 14, Samsung SM-A326U. Reproduces with
any List using .onMove on a dark background.

Start in Sources/SkipUI/SkipUI/Containers/List.swift at RenderReorderableItem and trace how dragging is supplied by ReorderableItem and how onDragEnd commits the move. Review System/Gesture.swift for the documented gesture callback behavior, then reproduce List reordering on a dark background. Done means the active row has a visible drag affordance without changing drop behavior, with the chosen treatment or API direction clearly settled.