Kernel HTTP API

Fastest non-interactive path: create or recover a key using Kernel's Auth.md flow, which emails a one-time code and returns the plaintext API key once. If you already use the CLI, you can first run kernel login, then mint and manage keys with `kernel api-keys create`; the docs also note keys can be managed from the dashboard. Store the resulting sk_... secret securely; Kernel only returns plaintext keys on create/rotate.