docs(readme): fix local-LLM setup command (npx tempest config → npx tempest)

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`.

README.md

@@ -87,7 +87,7 @@ Or run it **fully offline** on your own model — no key, no cloud. Defaults to
 ollama serve && ollama pull llama3                          # or an OpenAI-compatible server
 export TEMPEST_LOCAL_BASE_URL=http://localhost:11434/api    # LM Studio: http://localhost:1234/v1
 export TEMPEST_LOCAL_MODEL=llama3
-npx tempest config                                          # → "Change default provider" → local
+npx tempest                                                 # → "Change default provider" → local
 ```
 
 Tool-calling works on any local model (it's driven over text), so the Arsenal runs even on models without native function-calling.