bug: Default model was not recommended due to capitalization

[gabrielle-ong]

Cortex version

cortex-beta v1.0.0-rc1

Describe the Bug

When reading from metadata.yml, default branch was not detected due to 34B vs 34b

Existing branches may have inconsistent capitalization - can we make parsing it case-insensitive? Linked to implementation in #1418

Steps to Reproduce

No response

Screenshots / Logs

No response

What is your OS?

• [X] MacOS
• [ ] Windows
• [ ] Linux

What engine are you running?

• [X] cortex.llamacpp (default)
• [ ] cortex.tensorrt-llm (Nvidia GPUs)
• [ ] cortex.onnx (NPUs, DirectML)