DeepSeek: DeepSeek V3 docs materially updated

* The deepseek-chat and deepseek-reasoner correspond to the model version DeepSeek-V3.2 (128K context limit), which differs from the APP/WEB version. deepseek-chat is the non-thinking mode of DeepSeek-V3.2 and deepseek-reasoner is the thinking mode of DeepSeek-V3.2.