Function redistribute_ui_layers 

pub fn redistribute_ui_layers(
    extracted: Res<'_, ExtractedUiLayers>,
    phases: ResMut<'_, ViewSortedRenderPhases<TransparentUi>>,
    draw_functions: Res<'_, DrawFunctions<TransparentUi>>,
    composite_pipeline: Option<Res<'_, LayerCompositePipeline>>,
    specialized: ResMut<'_, SpecializedRenderPipelines<LayerCompositePipeline>>,
    pipeline_cache: Res<'_, PipelineCache>,
)

Moves promoted subtrees’ phase items from the camera’s UI phase into their layer’s synthetic phase, then injects one composite quad per layer. Runs after queueing, before the stock sort (which then sorts every phase, stolen items keeping their global stack-index sort keys).