Setup offers Codex #396

Parent

#136

What to build

Setup can choose Codex as the Harness when it's installed. Its questions show what Codex offers.

• When Codex is installed, it's no longer refused in the Harness question.
• For Codex, the Model question lists the models codex debug models offers, as slug and display name. The Effort question lists the levels the chosen Model supports.
• Answers are checked and translated as a Run checks them. GPT-6.1-Sol and Max are written as gpt-6.1-sol and max, and an unknown Model or an unsupported Effort is asked again.
• With only Codex installed, Codex is the default answer.

Acceptance criteria

• With codex on PATH, Setup accepts Codex as the Harness. With only codex installed, it's the default answer.
• The Model question lists Codex's models, and the Effort question lists the chosen Model's levels.
• Display names and capitalised efforts are written to the User config as slugs and lowercase.
• An unknown Model, or an Effort the Model doesn't support, is asked again with the valid choices shown.

Blocked by

• Setup asks for the Harness, Model and Effort #393
• Run a Command's sessions on Codex #394