feat(web): Insert newline on Alt+Enter in chat box

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: brendan-kellam

packages/web/src/features/chat/components/chatBox/chatBox.tsx

@@ -215,6 +215,12 @@ const ChatBoxComponent = ({
                         break;
                     }
 
+                    if (event.altKey) {
+                        event.preventDefault();
+                        editor.insertBreak();
+                        break;
+                    }
+
                     event.preventDefault();
                     onSubmit();
                     break;