This PR does the following: * Adds the ability to paste or type an API key. * Removes the `preferred_auth_method` config option. The last login method is always persisted in auth.json, so this isn't needed. * If OPENAI_API_KEY env variable is defined, the value is used to prepopulate the new UI. The env variable is otherwise ignored by the CLI. * Adds a new MCP server entry point "login_api_key" so we can implement this same API key behavior for the VS Code extension. <img width="473" height="140" alt="Screenshot 2025-09-04 at 3 51 04 PM" src="https://github.com/user-attachments/assets/c11bbd5b-8a4d-4d71-90fd-34130460f9d9" /> <img width="726" height="254" alt="Screenshot 2025-09-04 at 3 51 32 PM" src="https://github.com/user-attachments/assets/6cc76b34-309a-4387-acbc-15ee5c756db9" />