fix(opencode): allow gpt-5.5 in Codex OAuth model list

[mattyatea]

Issue for this PR

Related to #24036
Related to #24039

Type of change

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

What does this PR do?

Adds gpt-5.5 to the explicit Codex OAuth allowed model list for OpenAI. models.dev already includes the model, and this keeps the Codex OAuth allowlist aligned with that supported model surface.

How did you verify your code works?

• bun test test/plugin/codex.test.ts
• bun typecheck from packages/opencode
• push hook: bun turbo typecheck
• macOS CLI build: bun run build --single from packages/opencode with dist/opencode-darwin-arm64/bin/opencode --version smoke test passing

Screenshots / recordings

No UI change.

Checklist

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

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[rekram1-node]

it's already supported

[nexxai]

@rekram1-node You say it's already supported and I even see the PR that you created where support for 5.5 was merged into the dev branch but if you look at the branch now, 5.5 simply is not there. Am I going insane or did the change somehow get lost/overwritten?