OLLAMA_HOST

Also written: OLLAMA_MODELS, OLLAMA_NO_CLOUD, OLLAMA_CONTEXT_LENGTH

Ollama environment variables: `OLLAMA_HOST` sets the address it listens on (and where the Python package looks), `OLLAMA_MODELS` the model folder, `OLLAMA_NO_CLOUD` turns cloud features off, and `OLLAMA_CONTEXT_LENGTH` sets the default context.