fix(openai): support websocket custom base URLs

[Tarquinen]

Issue for this PR

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Allows codex oauth websocket to handle custom openai baseURL that use /responses path

How did you verify your code works?

added logs to see I was connected through websockets for both default openai and through a custom baseURL, see below

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate Found

PR #29394: feat(opencode): add experimental OpenAI Responses WebSocket
#29394

Why it's related:

PR #29394 adds the experimental OpenAI Responses WebSocket feature, while PR #29636 (current) fixes support for custom OpenAI base URLs with that WebSocket implementation. These PRs are closely related—the current fix likely addresses an issue discovered in PR #29394's feature. You may want to check if #29394 is already merged and whether this fix should be incorporated there or if they should be reviewed together.