eb5b1b627f
This PR introduces a new `Auth Storage` abstraction layer that takes care of read, write, and load of auth tokens based on the AuthCredentialsStoreMode. It is similar to how we handle MCP client oauth [here](https://github.com/openai/codex/blob/main/codex-rs/rmcp-client/src/oauth.rs). Instead of reading and writing directly from disk for auth tokens, Codex CLI workflows now should instead use this auth storage using the public helper functions. This PR is just a refactor of the current code so the behavior stays the same. We will add support for keyring and hybrid mode in follow-up PRs. I have read the CLA Document and I hereby sign the CLA