No OAuth option for ChatGPT Plus / Codex subscription — only API key is available

## Summary

OpenClaw supports OAuth authentication for subscription plans such as ChatGPT Plus (Codex OAuth). However, when deploying via Cloudflare using **moltworker**, I noticed that this authentication method is not available — only API key authentication is offered.

## Expected Behavior

OAuth authentication for subscription plans (ChatGPT Plus, Claude Max, etc.) should be available, consistent with the standard OpenClaw onboarding wizard.

## Why This Matters

The majority of current OpenClaw users are likely using — or wanting to use — subscription-based authentication rather than pay-per-token API keys. Subscription plans like ChatGPT Plus offer a fixed monthly cost ($20/month), which makes budgeting predictable and eliminates the risk of unexpected API charges.

## Question

Is there a plan to support OAuth authentication for subscription plans in moltworker? If so, is there a rough timeline or any workaround in the meantime?

The issue names no implementation files or tests. Start by tracing moltworker's current API-key authentication path and comparing it with the OpenClaw onboarding flow for ChatGPT Plus and Claude Max OAuth; done means subscription authentication is available in the Cloudflare deployment and its relevant behavior is tested.

Written by the indexing model from the issue text.