The quickstart tells users to run `npx tempest config` to switch to the local
provider, but there is no `config` subcommand — the CLI exposes `interactive`
(default), `setup`, `status`, `test`, and `models`. The "Change default
provider" flow lives in the default `interactive` command, so the correct
invocation is `npx tempest`.
Add a first-class `gemini` provider so operators can drive missions with a
direct GEMINI_API_KEY, instead of only reaching Gemini through OpenRouter.
Gemini is wired exactly like xAI: dispatched through OpenAIAdapter against
Google's OpenAI-compatible surface. The base URL is
https://generativelanguage.googleapis.com/v1beta/openai — the `/openai`
segment is required because OpenAIAdapter posts to `${baseUrl}/chat/completions`;
without it requests hit `/v1beta/chat/completions`, which Google does not serve.
Wires the provider through the type union, adapter factory, config
(interface, defaults, model catalog, key env map, getLLMConfig, fallback
chain, redaction, .env template), and adds regression tests pinning the
`/openai` base-URL segment.