Add default conversation title

internal/service/static/js/ui.js

@@ -39,9 +39,9 @@ export function extractText(content) {
     .join('\n');
 }
 
-// Conversations created from this UI have no title. Their label
-// falls back to the creation date, so the picker stays readable.
-// Both dates render in the browser locale.
+// CONVERSATION_DATE formats conversation timestamps in the browser
+// locale. Until the server sets a title from the first user message, an
+// untitled conversation uses its formatted creation date as its label.
 const CONVERSATION_DATE = new Intl.DateTimeFormat(undefined, {
   dateStyle: 'medium',
   timeStyle: 'short',