Improve chat rendering and generation summaries

src/server.rs

@@ -945,6 +945,7 @@ mod tests {
         let active = crate::runtime::ActiveGeneration {
             events: receiver,
             cancel: Arc::new(AtomicBool::new(false)),
+            started_at: std::time::Instant::now(),
         };
         let producer = thread::spawn(move || {
             thread::sleep(Duration::from_millis(25));