Add information about ollama - document it as an available provider a…

…nd provide clearer troubleshooting help. (#1235)

* Add information about ollama.

Thanks to @krassowski for pointing out the issue.  See #840 for additional
suggestions on how to improve the UX for unlisted models; for now this only
addresses clarifying the docs.

* add explicit pip command for installation

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

docs/source/users/index.md

@@ -439,7 +439,22 @@ models.
 
 ### Ollama usage
 
-To get started, follow the instructions on the [Ollama website](https://ollama.com/) to set up `ollama` and download the models locally. To select a model, enter the model name in the settings panel, for example `deepseek-coder-v2`.
+To get started, follow the instructions on the [Ollama website](https://ollama.com/) to set up `ollama` and download the models locally. To select a model, enter the model name in the settings panel, for example `deepseek-coder-v2`.  You can see all locally available models with  `ollama list`.
+
+For the Ollama models to be available to JupyterLab-AI, your Ollama server _must_ be running. You can check that this is the case by calling `ollama serve` at the terminal, and should see something like:
+
+```
+$ ollama serve
+Error: listen tcp 127.0.0.1:11434: bind: address already in use
+```
+
+In some platforms (e.g. macOS or Windows), there may also be a graphical user interface or application that lets you start/stop the Ollama server from a menu.
+
+:::{tip}
+If you don't see Ollama listed as a model provider in the Jupyter-AI configuration box, despite confirming that your Ollama server is active, you may be missing the  [`langchain-ollama` python package](https://pypi.org/project/langchain-ollama/) that is necessary for Jupyter-AI to interface with Ollama, as indicated in the [model providers](#model-providers) section above.
+
+You can install it with `pip install langchain-ollama` (as of Feb'2025 it is not available on conda-forge).
+:::
 
 ### vLLM usage
 
@@ -710,6 +725,7 @@ We currently support the following language model providers:
 - `cohere`
 - `huggingface_hub`
 - `nvidia-chat`
+- `ollama`
 - `openai`
 - `openai-chat`
 - `sagemaker-endpoint`