Add cliBin and cliExtraArgs fields to the codex Agent, parsed from the
new cli_path option (e.g. cli_path = "omx" or cli_path = "omx --flag").
The binary is used for both LookPath validation and subprocess execution,
allowing users to run codex-compatible CLIs like omx through cc-connect.
Closes#545
Co-authored-by: Claude <noreply@anthropic.com>