Update chat_template (always include system placeholder)

tokenizer_config.json

@@ -2093,7 +2093,7 @@
     }
   },
   "bos_token": "<s>",
-  "chat_template": "{% if not add_generation_prompt is defined %}{% set add_generation_prompt = false %}{% endif %}{% for message in messages %}{{'<|im_start|>' + message['role'] + '\n' + message['content'] + '<|im_end|>' + '\n'}}{% endfor %}{% if add_generation_prompt %}{{ '<|im_start|>assistant\n' }}{% endif %}",
+  "chat_template": "{%- set system_message = namespace(content='') -%}{%- if messages[0]['role'] == 'system' -%}{%- set system_message.content = messages[0]['content'] -%}{%- endif -%}<|im_start|>system\n{{ system_message.content }}<|im_end|>\n{% for message in messages -%}{%- if message['role'] != 'system' %}<|im_start|>{{ message['role'] }}\n{{ message['content'] }}<|im_end|>\n{% endif -%}{%- endfor -%}",
   "clean_up_tokenization_spaces": false,
   "eos_token": "<|im_end|>",
   "legacy": true,