[Epic] Open Source Models Support for CUGA

[adiasaf]

What You Want

Add comprehensive support for open source language models in CUGA, enabling users to run the agent with locally-hosted or open-source model providers as alternatives to proprietary models.

Initial Model Support

The epic should include support for the following open source models:

1. GPT-OSS-20B - Open source GPT variant with 20B parameters
2. Nemotron 3 Super - NVIDIA's advanced instruction-following model
3. Gemma 4 34B - Google's latest Gemma model with 34B parameters
4. Mistral Small 4 - Mistral AI's efficient small model