Headless pictures draw on the GPU, with the viewport's pipelines (CPU rasterizer as last tier) (#1555)

Thanks @jyviko.

xtask/src/layers.rs

@@ -56,8 +56,9 @@ pub const TABLE: &[(&str, Class)] = &[
 ];
 
 /// Explicit orderings *within* a layer (earlier may be used by later).
-/// The viewport draws display plans the GPU crate evaluates.
-pub const INTRA_LAYER_ORDER: &[&[&str]] = &[&["gpu", "ui-egui"]];
+/// The viewport draws display plans the GPU crate evaluates and draws with its pipelines; the MCP
+/// server's tests draw screenshots with them.
+pub const INTRA_LAYER_ORDER: &[&[&str]] = &[&["gpu", "ui-egui"], &["gpu", "mcp"]];
 
 fn intra_layer_allowed(from: &str, to: &str) -> bool {
     let (from, to) = (short_name(from), short_name(to));