[FEATURE] codex integration

## Feature Description

I realize this will likely be marked as out of scope, but I figured I would try. Worst case, it'll stick around in closed issues as a warning to others.

I quite enjoyed this plugin up until I switched to codex recently. It would be nice to have it continue working, especially after I spent time setting things up.

Any effort here would be appreciated and I am happy to help test. Thank you!

No files, tests, or entry points are named. Begin by reviewing the existing Claude Code integration and determining how Codex should be supported; clarify the expected behavior and acceptance criteria with maintainers before implementation. Done means the plugin continues working for Codex users and the integration is covered by appropriate verification.

Written by the indexing model from the issue text.