perf(app): trim session render work (#16987)

packages/app/src/pages/session/message-timeline.tsx

@@ -764,6 +764,7 @@ export function MessageTimeline(props: {
                         "min-w-0 w-full max-w-full": true,
                         "md:max-w-200 2xl:max-w-[1000px]": props.centered,
                       }}
+                      style={{ "content-visibility": "auto", "contain-intrinsic-size": "auto 500px" }}
                     >
                       <Show when={commentCount() > 0}>
                         <div class="w-full px-4 md:px-5 pb-2">