Add EventDetailHeader component and fix EventViewer overflow

- Create standardized EventDetailHeader with title, timestamp, actions, and copyText props
- Fix EventViewer firstSlot overflow/scrolling issue
- Update GrpcResponsePane, WebsocketResponsePane, HttpResponseTimeline, and EventStreamViewer to use EventDetailHeader
- Fix Timeline title consistency when toggling Raw/Formatted views

src-web/components/core/AutoScroller.tsx

@@ -63,7 +63,7 @@ export function AutoScroller<T>({
   }, [autoScroll, data.length]);
 
   return (
-    <div className="h-full w-full relative grid grid-rows-[minmax(0,auto)_minmax(0,1fr)]">
+    <div className="h-full w-full relative grid grid-rows-[auto_minmax(0,1fr)]">
       {!autoScroll && (
         <div className="absolute bottom-0 right-0 m-2">
           <IconButton