## Why
This adds a checked-in Codex environment configuration so the repo
exposes a ready-to-run Codex action from the app environment metadata.
## What changed
- Added `.codex/environments/environment.toml` with a generated `Run`
action.
- The action runs the `codex` binary from `codex-rs/Cargo.toml` with
`mcp_oauth_credentials_store=file`.
## Verification
- Not run; configuration-only change.
