Add Codex CLI support to AIStack

[StudioEtrange]

Motivation

• Provide first-class support for a Codex CLI client in the same style as existing gemini/opencode integrations so users can install, configure and run Codex from aistack.
• Keep Codex lifecycle and configuration management consistent with other clients by adding launchers, path registration and managed defaults.

Description

• Added a Codex integration library lib/lib_codex.sh implementing paths, codex_install/codex_uninstall, launcher generation, and settings management with a managed block in the user config file.
• Added command entry lib/main_cx.sh providing the aistack cx subcommand with install, uninstall, configure, reset, register, unregister, show-config and launch behaviors modeled after oc/gc handlers.
• Wired Codex into the global runtime and uninstall flow by updating lib/lib.sh to call codex_path during initialization and to unregister Codex launchers during uninstall, and updated aistack to source lib_codex.sh and route the cx command.
• Added a default template pool/settings/codex/config.toml and a placeholder user doc doc/codex.md, and updated README.md to advertise Codex support.

Testing

• Ran a shell syntax check with bash -n aistack lib/lib.sh lib/lib_codex.sh lib/main_cx.sh and it completed successfully.
• Ran ./aistack help >/tmp/aistack_help.txt and verified presence of Codex help lines with rg -n "cx : codex|aistack cx", which succeeded.

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Codex Task

[StudioEtrange]

@codex

[chatgpt-codex-connector]

To use Codex here, create a Codex account and connect to github.