- Configuration file is now placed in XDG_CONFIG_HOME/codex/config.toml by default for versions >=0.2.0 when preferXdgDirectories is enabled.
- Falls back to ~/.codex/config.yaml for versions <0.2.0 and to ~/.codex/config.toml when preferXdgDirectories is disabled
- Sets CODEX_HOME environment variable to $XDG_CONFIG_HOME/codex when using XDG directories.
- Updated tests to verify XDG directory behavior and environment variable presence.