fix(ccswitch): default OpenAI import model to gpt-5.5

[skyswordw]

Background

The Codex "Use key" config template already defaults model and review_model to gpt-5.5, but the CC Switch import path still defaults OpenAI/Codex imports to gpt-5.4.

This makes the two user-facing setup paths produce different default Codex models.

Summary

• update the OpenAI CC Switch Codex import default model to gpt-5.5
• add an explicit test for the OpenAI CC Switch default model

Tests

• pnpm exec vitest run src/utils/__tests__/ccswitchImport.spec.ts

[github-actions]

All contributors have signed the CLA. ✅
_{Posted by the CLA Assistant Lite bot.}