feat: show favicons for external chat links

Adds DuckDuckGo favicon lookup for external URLs
Shows favicons in markdown and fetch tool link rows
Hides missing icons automatically

packages/ui/src/components/chat/MarkdownRendererImpl.tsx

@@ -17,7 +17,7 @@ import { Icon } from "@/components/icon/Icon";
 import { copyTextToClipboard } from '@/lib/clipboard';
 import { useI18n } from '@/lib/i18n';
 
-import { isExternalHttpUrl, isLoopbackHttpUrl, openExternalUrl } from '@/lib/url';
+import { getExternalFaviconUrl, isExternalHttpUrl, isLoopbackHttpUrl, openExternalUrl } from '@/lib/url';
 import { useOptionalThemeSystem } from '@/contexts/useThemeSystem';
 import { getDefaultTheme } from '@/lib/theme/themes';
 import { generateSyntaxTheme } from '@/lib/theme/syntaxThemeGenerator';
@@ -92,6 +92,27 @@ const useExternalLinkInteractions = ({
   }, [containerRef, enabled]);
 };
 
+const ExternalLinkFavicon: React.FC<{ href: string }> = ({ href }) => {
+  const [failed, setFailed] = React.useState(false);
+  const faviconUrl = React.useMemo(() => getExternalFaviconUrl(href), [href]);
+
+  if (!faviconUrl || failed) {
+    return null;
+  }
+
+  return (
+    <img
+      src={faviconUrl}
+      alt=""
+      aria-hidden="true"
+      loading="lazy"
+      decoding="async"
+      className="mr-1 inline-block size-4 rounded-sm align-[-0.1875em]"
+      onError={() => setFailed(true)}
+    />
+  );
+};
+
 // Table utility functions
 const extractTableData = (tableEl: HTMLTableElement): { headers: string[]; rows: string[][] } => {
   const headers: string[] = [];
@@ -935,15 +956,17 @@ const buildMarkdownComponents = ({
   },
   a({ href, children, ...props }) {
     const targetHref = href ?? '';
+    const isExternal = isExternalHttpUrl(targetHref);
     const isLoopback = onPreviewLoopback ? isLoopbackHttpUrl(targetHref) : false;
     return (
       <>
         <a
           {...props}
           href={href}
-          target={isExternalHttpUrl(targetHref) ? '_blank' : undefined}
-          rel={isExternalHttpUrl(targetHref) ? 'noopener noreferrer' : undefined}
+          target={isExternal ? '_blank' : undefined}
+          rel={isExternal ? 'noopener noreferrer' : undefined}
         >
+          {isExternal ? <ExternalLinkFavicon href={targetHref} /> : null}
           {children}
         </a>
         {isLoopback && onPreviewLoopback ? (