feat(cx): add GPT-5.5 Pro and GPT-5.4 Pro models to Codex provider #890

Summary

The Codex (cx) provider model list is missing gpt-5.5-pro and gpt-5.4-pro. These are distinct models available to ChatGPT Pro subscribers via the Codex backend (chatgpt.com/backend-api/codex/responses).

Context

OpenAI's model registry (models.dev) lists both as separate models with their own family (gpt-pro):

The opencode project dynamically discovers these via a regex filter (gpt-X.Y > 5.4) and shows them to OAuth users. 9Router's hardcoded list in open-sse/config/providerModels.js only has gpt-5.5 and gpt-5.4.

Expected

Add gpt-5.5-pro and gpt-5.4-pro to the cx provider model list so users with ChatGPT Pro subscriptions can route through them.

Notes

• These are Pro subscription tier models — they may not work for ChatGPT Plus users (only Pro). The executor shouldn't need changes since the model ID is passed through as-is.
• The existing withCodexReviewModels() wrapper should automatically generate -review variants for both.

cc @decolua