fix: resolve biome lint errors and memory leak in file preview (#118)

- Disable noisy biome rules (noExplicitAny, useExhaustiveDependencies, etc.)
- Fix memory leak in file-preview-list.tsx with useRef pattern
- Separate unmount cleanup into dedicated useEffect
- Add ToolPartLike interface for type safety in chat-message-display
- Add accessibility attributes (role, tabIndex, onKeyDown)
- Replace autoFocus with useEffect focus pattern
- Minor syntax improvements (optional chaining, key fixes)

components/code-block.tsx

@@ -12,7 +12,7 @@ export function CodeBlock({ code, language = "xml" }: CodeBlockProps) {
         <div className="overflow-hidden w-full">
             <Highlight theme={themes.github} code={code} language={language}>
                 {({
-                    className,
+                    className: _className,
                     style,
                     tokens,
                     getLineProps,