Refactor: Consolidate event viewers into unified EventViewer component

Migrate EventStreamViewer, HttpResponseTimeline, GrpcResponsePane, and
WebsocketResponsePane to use a shared EventViewer component with generic
event type support, render props for rows and details, and keyboard
navigation (↑/↓/j/k/Escape). This reduces duplication and provides a
consistent event viewing experience across all response types.

src-web/components/core/AutoScroller.tsx

@@ -1,4 +1,4 @@
-import { useVirtualizer } from '@tanstack/react-virtual';
+import { type Virtualizer, useVirtualizer } from '@tanstack/react-virtual';
 import type { ReactElement, ReactNode, UIEvent } from 'react';
 import { useCallback, useLayoutEffect, useRef, useState } from 'react';
 import { IconButton } from './IconButton';
@@ -7,9 +7,19 @@ interface Props<T> {
   data: T[];
   render: (item: T, index: number) => ReactElement<HTMLElement>;
   header?: ReactNode;
+  /** Make container focusable for keyboard navigation */
+  focusable?: boolean;
+  /** Callback to expose the virtualizer for keyboard navigation */
+  onVirtualizerReady?: (virtualizer: Virtualizer<HTMLDivElement, Element>) => void;
 }
 
-export function AutoScroller<T>({ data, render, header }: Props<T>) {
+export function AutoScroller<T>({
+  data,
+  render,
+  header,
+  focusable = false,
+  onVirtualizerReady,
+}: Props<T>) {
   const containerRef = useRef<HTMLDivElement>(null);
   const [autoScroll, setAutoScroll] = useState<boolean>(true);
 
@@ -20,6 +30,11 @@ export function AutoScroller<T>({ data, render, header }: Props<T>) {
     estimateSize: () => 27, // react-virtual requires a height, so we'll give it one
   });
 
+  // Expose virtualizer to parent for keyboard navigation
+  useLayoutEffect(() => {
+    onVirtualizerReady?.(rowVirtualizer);
+  }, [rowVirtualizer, onVirtualizerReady]);
+
   // Scroll to new items
   const handleScroll = useCallback(
     (e: UIEvent<HTMLDivElement>) => {
@@ -63,7 +78,12 @@ export function AutoScroller<T>({ data, render, header }: Props<T>) {
         </div>
       )}
       {header ?? <span aria-hidden />}
-      <div ref={containerRef} className="h-full w-full overflow-y-auto" onScroll={handleScroll}>
+      <div
+        ref={containerRef}
+        className="h-full w-full overflow-y-auto"
+        onScroll={handleScroll}
+        tabIndex={focusable ? 0 : undefined}
+      >
         <div
           style={{
             height: `${rowVirtualizer.getTotalSize()}px`,

src-web/components/core/EventViewer.tsx

@@ -0,0 +1,166 @@
+import type { Virtualizer } from '@tanstack/react-virtual';
+import type { ReactNode } from 'react';
+import { useCallback, useMemo, useRef, useState } from 'react';
+import { useEventViewerKeyboard } from '../../hooks/useEventViewerKeyboard';
+import { AutoScroller } from './AutoScroller';
+import { Banner } from './Banner';
+import { Separator } from './Separator';
+import { SplitLayout } from './SplitLayout';
+
+interface EventViewerProps<T> {
+  /** Array of events to display */
+  events: T[];
+
+  /** Get unique key for each event */
+  getEventKey: (event: T, index: number) => string;
+
+  /** Render the event row - receives event, index, isActive, and onClick */
+  renderRow: (props: {
+    event: T;
+    index: number;
+    isActive: boolean;
+    onClick: () => void;
+  }) => ReactNode;
+
+  /** Render the detail pane for the selected event */
+  renderDetail?: (props: { event: T; index: number }) => ReactNode;
+
+  /** Optional header above the event list (e.g., connection status) */
+  header?: ReactNode;
+
+  /** Error message to display as a banner */
+  error?: string | null;
+
+  /** Name for SplitLayout state persistence */
+  splitLayoutName: string;
+
+  /** Default ratio for the split (0.0 - 1.0) */
+  defaultRatio?: number;
+
+  /** Enable keyboard navigation (arrow keys) */
+  enableKeyboardNav?: boolean;
+
+  /** Loading state */
+  isLoading?: boolean;
+
+  /** Message to show while loading */
+  loadingMessage?: string;
+
+  /** Message to show when no events */
+  emptyMessage?: string;
+}
+
+export function EventViewer<T>({
+  events,
+  getEventKey,
+  renderRow,
+  renderDetail,
+  header,
+  error,
+  splitLayoutName,
+  defaultRatio = 0.4,
+  enableKeyboardNav = true,
+  isLoading = false,
+  loadingMessage = 'Loading events...',
+  emptyMessage = 'No events recorded',
+}: EventViewerProps<T>) {
+  const [activeIndex, setActiveIndex] = useState<number | null>(null);
+  const containerRef = useRef<HTMLDivElement>(null);
+  const virtualizerRef = useRef<Virtualizer<HTMLDivElement, Element> | null>(null);
+
+  const activeEvent = useMemo(
+    () => (activeIndex != null ? events[activeIndex] : null),
+    [activeIndex, events],
+  );
+
+  // Check if the event list container is focused
+  const isContainerFocused = useCallback(() => {
+    return containerRef.current?.contains(document.activeElement) ?? false;
+  }, []);
+
+  // Keyboard navigation
+  useEventViewerKeyboard({
+    totalCount: events.length,
+    activeIndex,
+    setActiveIndex,
+    virtualizer: virtualizerRef.current,
+    isContainerFocused,
+    enabled: enableKeyboardNav,
+  });
+
+  // Handle virtualizer ready callback
+  const handleVirtualizerReady = useCallback(
+    (virtualizer: Virtualizer<HTMLDivElement, Element>) => {
+      virtualizerRef.current = virtualizer;
+    },
+    [],
+  );
+
+  // Toggle selection on click
+  const handleRowClick = useCallback(
+    (index: number) => {
+      setActiveIndex((prev) => (prev === index ? null : index));
+    },
+    [],
+  );
+
+  if (isLoading) {
+    return <div className="p-3 text-text-subtlest italic">{loadingMessage}</div>;
+  }
+
+  if (events.length === 0 && !error) {
+    return <div className="p-3 text-text-subtlest italic">{emptyMessage}</div>;
+  }
+
+  return (
+    <div ref={containerRef} className="h-full">
+      <SplitLayout
+        layout="vertical"
+        name={splitLayoutName}
+        defaultRatio={defaultRatio}
+        minHeightPx={10}
+        firstSlot={() => (
+          <>
+            {header}
+            <AutoScroller
+              data={events}
+              focusable={enableKeyboardNav}
+              onVirtualizerReady={handleVirtualizerReady}
+              header={
+                error && (
+                  <Banner color="danger" className="m-3">
+                    {error}
+                  </Banner>
+                )
+              }
+              render={(event, index) => (
+                <div key={getEventKey(event, index)}>
+                  {renderRow({
+                    event,
+                    index,
+                    isActive: index === activeIndex,
+                    onClick: () => handleRowClick(index),
+                  })}
+                </div>
+              )}
+            />
+          </>
+        )}
+        secondSlot={
+          activeEvent != null && renderDetail
+            ? () => (
+                <div className="grid grid-rows-[auto_minmax(0,1fr)]">
+                  <div className="pb-3 px-2">
+                    <Separator />
+                  </div>
+                  <div className="mx-2 overflow-y-auto">
+                    {renderDetail({ event: activeEvent, index: activeIndex! })}
+                  </div>
+                </div>
+              )
+            : null
+        }
+      />
+    </div>
+  );
+}

src-web/components/core/EventViewerRow.tsx

@@ -0,0 +1,38 @@
+import classNames from 'classnames';
+import { format } from 'date-fns';
+import type { ReactNode } from 'react';
+
+interface EventViewerRowProps {
+  isActive: boolean;
+  onClick: () => void;
+  icon: ReactNode;
+  content: ReactNode;
+  timestamp: string;
+}
+
+export function EventViewerRow({
+  isActive,
+  onClick,
+  icon,
+  content,
+  timestamp,
+}: EventViewerRowProps) {
+  return (
+    <div className="px-1">
+      <button
+        type="button"
+        onClick={onClick}
+        className={classNames(
+          'w-full grid grid-cols-[auto_minmax(0,1fr)_auto] gap-2 items-center text-left',
+          'px-1.5 h-xs font-mono text-editor cursor-default group focus:outline-none focus:text-text rounded',
+          isActive && '!bg-surface-active !text-text',
+          'text-text-subtle hover:text',
+        )}
+      >
+        {icon}
+        <div className="w-full truncate">{content}</div>
+        <div className="opacity-50">{format(`${timestamp}Z`, 'HH:mm:ss.SSS')}</div>
+      </button>
+    </div>
+  );
+}