chat_template: add enable_thinking flag (sync with JANG_2L)

chat_template.jinja

@@ -155,5 +155,9 @@
 
 {#- Generation prompt -#}
 {%- if add_generation_prompt -%}
-{{- ']~b]ai' ~ '\n' ~ '<think>' ~ '\n' }}
+{{- ']~b]ai' ~ '\n' }}
+    {%- if enable_thinking is defined and enable_thinking is false -%}
+    {%- else -%}
+    {{- '<think>' ~ '\n' }}
+    {%- endif -%}
 {%- endif -%}