feat(examples): polish workout phone UI

Give the workout exemplar a durable gym-floor command-slate direction, serve focused CSS, keep the first viewport centered on one action, and extend the HTTP E2E to verify stylesheet delivery.

req: examples/001

req: local/001

req: local/003

req: host/002

examples/workout/src/main.rs

@@ -24,6 +24,7 @@ async fn main() {
 pub fn app(state: AppState) -> Router {
     Router::new()
         .route("/", get(page).post(interact))
+        .route("/workout.css", get(workout_css))
         .route(runtime_js_path(), get(runtime))
         .with_state(state)
 }
@@ -41,6 +42,13 @@ async fn interact(
     request.dispatch_async(workout_app::registry(state)).await
 }
 
+async fn workout_css() -> impl IntoResponse {
+    (
+        [("content-type", "text/css; charset=utf-8")],
+        include_str!("../templates/workout.css"),
+    )
+}
+
 async fn runtime() -> impl IntoResponse {
     runtime_js()
 }