CompletionUsage tokens are defined as u32, but tokens can be negative

[nemosupremo]

When using the o3 model I'm coming across an issue where deserialization fails because the tokens returned is negative:

{
   "usage": {
       "prompt_tokens": 1151,
       "completion_tokens": -35,
       "total_tokens": 1116
   }
}

https://docs.rs/async-openai/latest/async_openai/types/struct.CompletionUsage.html#structfield.total_tokens

CompletionUsage is defined as u32, however the openai spec does not assert that these values are unsigned.