perf(app): better session stream rendering

packages/ui/src/components/session-turn.tsx

@@ -457,9 +457,16 @@ export function SessionTurn(
   })
 
   createEffect(() => {
-    const timer = setInterval(() => {
+    const update = () => {
       setStore("duration", duration())
-    }, 1000)
+    }
+
+    update()
+
+    // Only keep ticking while the active (in-progress) turn is running.
+    if (!working()) return
+
+    const timer = setInterval(update, 1000)
     onCleanup(() => clearInterval(timer))
   })
 
@@ -495,6 +502,11 @@ export function SessionTurn(
     }
   })
 
+  onCleanup(() => {
+    if (!statusTimeout) return
+    clearTimeout(statusTimeout)
+  })
+
   return (
     <div data-component="session-turn" class={props.classes?.root} ref={setRootRef}>
       <div