Litellm provider using openai model name defaults

[myaple]

Describe the bug

The litellm provider uses crates/goose/src/providers/formats/openai.rs as it's create_request (https://github.com/block/goose/blob/main/crates/goose/src/providers/litellm.rs#L170), but this create_request function does very specific openai processing, like here: https://github.com/block/goose/blob/main/crates/goose/src/providers/formats/openai.rs#L580

This means that if my litellm proxy has a model name that starts with "o", like "open-mistral-small-3.1", then it will send a reasoning_effort parameter regardless of whether or not it's a reasoning model.

To Reproduce
Steps to reproduce the behavior:

1. Stand up litellm with a model that starts with "o"
2. Send a request through goose
3. See that it sends a reasoning_effort parameter regardless of model

I've written a quick test for this behavior that fails on the current main branch: https://github.com/myaple/goose/blob/myaple/litellm-reasoning-bug/crates/goose/src/providers/litellm.rs#L339

Expected behavior
Reasoning parameters should only be sent to be models that support reasoning. Additionally, there should be an environment variable to override the reasoning parameter for the openai models or disable it completely.

Please provide following information:

• OS & Arch: ubuntu 24
• Interface: cli
• Version: 1.5.0
• Extensions enabled: n/a
• Provider & Model: litellm, open-mistral-small-3.1

[myaple]

I'm more than happy to give this issue a shot if you guys would like. My initial idea would be to add a parameter to the create_request function that takes in a reasoning effort override of high, medium, low, or disabled, and sets the reasoning effort appropriately without doing the model based parsing. This could then be passed in as a configuration parameter like GOOSE_REASONING_EFFORT if you'd like it done at a global level, or LITELLM_REASONING_EFFORT for provider level.

We could also create a new create_request specifically for litellm, but I think it'd be easier in the long run to leave the openai format alone until otherwise necessary rather than duplicate code.