[feature request] Add support for Chain of Thought (CoT) from deepseek-r1

[Rianico]

Hello everyone, I think the CoT of deepseek-r1 is significantly helpful for users to understand how the model solves the problem and can help us overcome the LLM hallucinations to some extent.

Currently the llm CLI just print the final output from llm, I think it's a cool feature if the cli can print the CoT.

According to the official document of Deepseek, the CoT is stored by the reasoning_content, which is at the same level as the content field, just like below:

reasoning_content = response.choices[0].message.reasoning_content
content = response.choices[0].message.content