Support jinja extra template kwargs (Qwen3 enable_thinking feature), from command line and from client

[matteoserva]

This PR implements handling additional jinja parameters.
Used for example to set enable_thinking in Qwen3 models.

The official template is still partially compatible. I modified it to use only supported features.
It's here: https://pastebin.com/16ZpCLHk
And should be loaded with llama-server --jinja --chat-template-file {template_file}

It fixes #13160 and #13189

Test it with:

• enable_thinking=false. Expected: {"prompt":"\n<|im_start|>user\nGive me a short introduction to large language models.<|im_end|>\n<|im_start|>assistant\n<think>\n\n</think>\n\n"}

curl http://localhost:8080/apply-template -H "Content-Type: application/json" -d '{
  "model": "Qwen/Qwen3-8B",
  "messages": [
    {"role": "user", "content": "Give me a short introduction to large language models."}
  ],
  "temperature": 0.7,
  "top_p": 0.8,
  "top_k": 20,
  "max_tokens": 8192,
  "presence_penalty": 1.5,
  "chat_template_kwargs": {"enable_thinking": false}
}'

• enable_thinking=true

curl http://localhost:8080/apply-template -H "Content-Type: application/json" -d '{
  "model": "Qwen/Qwen3-8B",
  "messages": [
    {"role": "user", "content": "Give me a short introduction to large language models."}
  ],
  "temperature": 0.7,
  "top_p": 0.8,
  "top_k": 20,
  "max_tokens": 8192,
  "presence_penalty": 1.5,
  "chat_template_kwargs": {"enable_thinking": true}
}'

• enable_thinking undefined

curl http://localhost:8080/apply-template -H "Content-Type: application/json" -d '{
  "model": "Qwen/Qwen3-8B",
  "messages": [
    {"role": "user", "content": "Give me a short introduction to large language models."}
  ],
  "temperature": 0.7,
  "top_p": 0.8,
  "top_k": 20,
  "max_tokens": 8192,
  "presence_penalty": 1.5
}'

[rhjdvsgsgks]

can you add chat_template_kwargs to cli argument as well?

[matteoserva]

can you add chat_template_kwargs to cli argument as well?

I added it. I tested it using updated command (You might want to check the escaping of the double quotes):
--chat_template_kwargs "{\"enable_thinking\":false}" --jinja --chat-template-file qwen/qwen3_template.txt

[neolee]

Very useful for Qwen3 series. +1 for this feature!