Allow configurable reasoning efforts for Review Mode

What feature would you like to see?

The reasoning effort for the /review command was hardcoded to Low in this PR: https://github.com/openai/codex/pull/3701

From the PR alone, it's not clear why the review mode reasoning effort was set to Low. Proposing to allow a user-configurable reasoning effort, either by:

1. Inheriting the current reasoning effort from the thread's config.model in codex-rs/core/src/codex.rs
2. Creating a user preference for review mode reasoning effort in config.toml
3. (if it's preferred to not allow configurability): At minimum, consider bumping the reasoning effort to Medium for more dynamic reasoning

From a local POC, it seems like approach 1 works well and creates much more comprehensive reviews than before (gpt-5.1-codex-max, xhigh effort inherited)

I'd be happy to raise a PR for this, seeking alignment first.

Additional information

_No response_