[deepseek-chat] Context window length is no longer accurate

[0x1eef]

Apologies if this has been opened elsewhere, but I couldn't find it.

About

The deepseek-chat context window is 131072 tokens, not 1280000.
Here's the error:

 {"error":{"message":"This model's maximum context length is 131072 tokens. However, you requested 131749 tokens (131749 in the messages, 0 in the completion). Please reduce the length of the messages or completion.","type":"invalid_request_error","param":null,"code":"invalid_request_error"}}

[seffhunnn]

I’d like to work on this.

[seffhunnn]

Opened PR #1342 to fix this.