What this PR does

Issue #70 ran into an issue using a project ID and organization ID with the OpenAI LLM-as-judge provider. In my own testing here, I was not using either env var and simply hadn't supported them. This PR adds support for:

• OPENAI_ORG_ID - sent as a OpenAI-Organization header
• OPENAI_PROJECT_ID - sent as OpenAI-Project header

This covers the three auth headers described in the OpenAI Developers Authentication documentation, and matches the OpenAI Python SDK env var naming.

How to test

The PR adds new tests in judge/client_test.go specifically for cases where:

• The env vars are present or omitted
• If a non-OpenAI baseURL is provided, as when using the API with Ollama, we should not send the headers even if the env vars are set

Checklist

• Tests pass locally (go test -race ./... -count=1)
• Lint passes locally (golangci-lint run)
• New functionality includes tests
• Breaking changes are noted above (if any)