Make the Rust client the sole app

docs/SCROLL.md

@@ -235,7 +235,7 @@ without a scroll-widget special case.
 
 ## The transcript's wiring
 
-`app-rust/src/ui/mod.rs`, `build_tree`.
+`app/src/ui/mod.rs`, `build_tree`.
 
 The transcript registers the wheel **by hand rather than calling
 `LazySpan::scrollable()`**, and this is not an oversight. That helper also