deepseek-chat and deepseek-reasoner upgraded to DeepSeek-V3.1-Terminus

Both deepseek-chat and deepseek-reasoner have been upgraded to DeepSeek-V3.1-Terminus. deepseek-chat corresponds to DeepSeek-V3.1-Terminus's non-thinking mode, while deepseek-reasoner corresponds to its thinking mode.

This update maintains the model's original capabilities while addressing issues reported by users, including:

• Language consistency: Reduced occurrences of Chinese-English mixing and occasional abnormal characters;
• Agent capabilities: Further optimized the performance of the Code Agent and Search Agent.