Primitives · a raise keeps its state under its owner's id

A raise inside another was namespaced by its place in the layer's
queue, so one that came before it moved its id path and rebuilt its
keyed state and focus: an open date popup would lose its month when a
tip appeared. raise now takes its owner's id and draws under it, and
float and float_height pass the owner's id on from every call site.
A test holds a focused box in a raise while another comes before it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/primitives/backdrop.rs

@@ -76,12 +76,13 @@ impl RenderOnce for Backdrop {
                 scrim.on_mouse_down(MouseButton::Left, move |_, window, cx| dismiss(window, cx))
             })
             .with_animation(
-                self.id,
+                self.id.clone(),
                 Animation::new(fade).with_easing(motion::ease_out_cubic),
                 |scrim, t| scrim.opacity(t),
             );
 
         raise(
+            (self.id, "raised"),
             anchored().position(Point::default()).child(
                 div()
                     .relative()