{#
  One exchange: the user's message plus the empty assistant bubble that will
  stream into it. Returned by POST /api/chats/{id}/messages and appended to the
  thread in a single swap, so the pair always arrives together.
#}
{% with message = user_message %}
  {% include "chat/_message.html" %}
{% endwith %}
{% with message = assistant_message %}
  {% include "chat/_message.html" %}
{% endwith %}