Add packages: tools on every launcher's PATH
Add companions: every launcher of an environment callable from its sessions
Export AGENT_ENV_LAUNCHER, the launcher's command name
Add example consumer flakes
Add real Codex integration check
Add behaviour checks with stub agents
Add flake with a default environment without skills
Add library: mkEnvironment, mkSkill and mkSkillModule
Add launchers with a state dir per login
Add Claude Code and Codex agent modules
Add core module: instruction fragments and skill closure