Add scoped overlay hosts

app-rust/tests/top_edge.rs

@@ -14,7 +14,7 @@ fn opened() -> (Harness, ai_app::ui::TranscriptScreen) {
         .span(Dir::DOWN)
         .add_strong(&mut h.rsc)
         .any();
-    h.state.set_root(root);
+    h.state.set_root(&mut h.rsc, root);
     h.frame(0);
     h.frame(PHONE_FRAME_MS);
     (h, opened.screen)