## Summary
Adds the missing `xhigh` reasoning level everywhere it should have been
documented, and makes clear it only works with `gpt-5.1-codex-max`.
## Changes
* `docs/config.md`
* Add `xhigh` to the official list of reasoning levels with a note that
`xhigh` is exclusive to Codex Max.
* `docs/example-config.md`
* Update the example comment adding `xhigh` as a valid option but only
for Codex Max.
* `docs/faq.md`
* Update the model recommendation to `GPT-5.1 Codex Max`.
* Mention that users can choose `high` or the newly documented `xhigh`
level when using Codex Max.
41760f8a09