fix(openai): openai ChatGPT OAuth requests using Zen API key - #49849

Hey! Your PR title fix openai ChatGPT OAuth requests using Zen API key doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

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

Confirming this bug on v2.0.12 (also reproduced on v2.0.8) - Linux, logged into the OpenCode Console and ChatGPT OAuth (chatgpt-headless, Plus plan) at the same time.

Every openai/* model fails with Provider request failed with HTTP 401, and re-authenticating OpenAI does not help.

I verified the diagnosis in this PR independently:

• The request does route to the correct endpoint — I proxied OpenCode's traffic: 10 connections to chatgpt.com:443, zero to api.openai.com. The chatgpt-account-id header is present.
• But the Authorization bearer is the Zen API key, not the ChatGPT OAuth token. Curling POST https://chatgpt.com/backend-api/codex/responses with my Zen key reproduces the exact failure: HTTP 401 {"message": "API keys are not supported by this endpoint.", "code": "api_key_not_supported"}.
• My ChatGPT OAuth token itself is fine — the same request with the OAuth bearer returns HTTP 200 and streams completions for gpt-5.5 and gpt-5.6-luna. So the stored credential is valid; the provider just never sends it, exactly as described here.
• I also checked the openai.ts source at the v2.0.11 and v2.0.12 tags: the integrationID pin from this PR is absent in both, so no released version contains the fix yet.

Happy to test a build with this merged.

It happens when BYOK key enabled in the OpenCode Console.

Removing my BYOK OpenAI account from the web console resolves it immediately, which points at the Console-supplied credential winning over the ChatGPT OAuth token.