Fix lint issues and improve EventViewer component

- Fix biome lint formatting issues
- Add onActiveIndexChange callback for controlled state
- Simplify WebsocketEventDetail to compute message internally
- Fix exhaustive deps warning in handleRowClick

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src-web/components/core/AutoScroller.tsx

@@ -1,4 +1,4 @@
-import { type Virtualizer, useVirtualizer } from '@tanstack/react-virtual';
+import { useVirtualizer, type Virtualizer } from '@tanstack/react-virtual';
 import type { ReactElement, ReactNode, UIEvent } from 'react';
 import { useCallback, useLayoutEffect, useRef, useState } from 'react';
 import { IconButton } from './IconButton';