Function transform_extracted_to_nodes 

pub fn transform_extracted_to_nodes(
    retained: ResMut<'_, RetainedScene>,
    previous: ResMut<'_, PreviousScene>,
    rects: Query<'_, '_, &ExtractedRect>,
    borders: Query<'_, '_, &ExtractedBorder>,
    shadows: Query<'_, '_, &ExtractedShadow>,
    outlines: Query<'_, '_, &ExtractedOutline>,
    texts: Query<'_, '_, &ExtractedText>,
    images: Query<'_, '_, (&ExtractedImage, Option<&ImageBlob>)>,
    svgs: Query<'_, '_, &SvgPayload>,
    clips: Query<'_, '_, &ExtractedClipBox>,
    scrollbars: Query<'_, '_, &ExtractedScrollbar>,
)

Builds a RetainedScene from the flat Extracted* components in the render world.

Walks every ExtractedRect/Shadow/Outline/Text/Image/Svg/ClipBox once, sorts the leaves by PaintOrder, folds the clip pairs around the leaves they enclose, and produces an Arc<Node::Container> containing the painter-ordered children. The previous frame’s root is moved into PreviousScene so the walker can diff against it.

Runs in crate::render_world::RenderStage::Prepare (registered by App::new).