Add CLI reference docs (#14)

* Add CLI reference doc

* touchups

* add helptext for download

docs/cli_reference.md

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+# Llama CLI Reference
+
+The `llama` CLI tool helps you setup and use the Llama toolchain & agentic systems. It should be available on your path after installing the `llama-toolchain` package.
+
+```
+$ llama --help
+
+Welcome to the Llama CLI
+
+Usage: llama [-h] {download,inference,model} ...
+
+
+Options:
+  -h, --help            Show this help message and exit
+
+
+Subcommands:
+  {download,inference,model}
+```
+
+## Step 1. Get the models
+
+First, you need models locally. You can get the models from [HuggingFace](https://huggingface.co/meta-llama) or [directly from Meta](https://llama.meta.com/llama-downloads/). The download command streamlines the process.
+
+
+```
+$ llama download --help
+usage: llama download [-h] [--hf-token HF_TOKEN] [--ignore-patterns IGNORE_PATTERNS] repo_id
+
+Download a model from the Hugging Face Hub
+
+positional arguments:
+  repo_id               Name of the repository on Hugging Face Hub eg. llhf/Meta-Llama-3.1-70B-Instruct
+
+options:
+  -h, --help            show this help message and exit
+  --hf-token HF_TOKEN   Hugging Face API token. Needed for gated models like Llama2. Will also try to read environment variable `HF_TOKEN` as default.
+  --ignore-patterns IGNORE_PATTERNS
+                        If provided, files matching any of the patterns are not downloaded. Defaults to ignoring safetensors files to avoid downloading duplicate weights.
+
+# Here are some examples on how to use this command:
+
+llama download --repo-id meta-llama/Llama-2-7b-hf --hf-token <HF_TOKEN>
+llama download --repo-id meta-llama/Llama-2-7b-hf --output-dir /data/my_custom_dir --hf-token <HF_TOKEN>
+HF_TOKEN=<HF_TOKEN> llama download --repo-id meta-llama/Llama-2-7b-hf
+
+The output directory will be used to load models and tokenizers for inference.
+```
+
+1. Create and get a Hugging Face access token [here](https://huggingface.co/settings/tokens)
+2. Set the `HF_TOKEN` environment variable
+
+```
+export HF_TOKEN=YOUR_TOKEN_HERE
+llama download meta-llama/Meta-Llama-3.1-70B-Instruct
+```
+
+## Step 2: Understand the models
+The `llama model` command helps you explore the model’s interface.
+
+```
+$ llama model --help
+usage: llama model [-h] {template} ...
+
+
+Describe llama model interfaces
+
+
+options:
+  -h, --help  show this help message and exit
+
+
+model_subcommands:
+  {template}
+
+
+Example: llama model <subcommand> <options>
+```
+
+You can run `llama model template` see all of the templates and their tokens:
+
+
+```
+$ llama model template
+
+
+system-message-builtin-and-custom-tools
+system-message-builtin-tools-only
+system-message-custom-tools-only
+system-message-default
+assistant-message-builtin-tool-call
+assistant-message-custom-tool-call
+assistant-message-default
+tool-message-failure
+tool-message-success
+user-message-default
+```
+
+And fetch an example by passing it to `--template`:
+
+```
+llama model template --template tool-message-success
+
+
+llama model template --template tool-message-success
+<|start_header_id|>ipython<|end_header_id|>
+
+
+completed
+[stdout]{"results":["something something"]}[/stdout]<|eot_id|>
+```
+
+## Step 3. Start the inference server
+
+Once you have a model, the magic begins with inference. The `llama inference` command can help you configure and launch the Llama Stack inference server.
+
+```
+$ llama inference --help
+
+
+usage: llama inference [-h] {start,configure} ...
+
+
+Run inference on a llama model
+
+
+options:
+  -h, --help         show this help message and exit
+
+
+inference_subcommands:
+  {start,configure}
+
+
+Example: llama inference start <options>
+```
+
+Run `llama inference configure` to setup your configuration at `~/.llama/configs/inference.yaml`. You’ll set up variables like:
+
+
+* the directory where you stored the models you downloaded from step 1
+* the model parallel size (1 for 8B models, 8 for 70B/405B)
+
+
+Once you’ve configured the inference server, run `llama inference start`. The model will load into GPU and you’ll be able to send requests once you see the server ready.
+
+
+If you want to use a different model, re-run `llama inference configure` to update the model path and llama inference start to start again.
+
+
+Run `llama inference --help` for more information.
+
+
+## Step 4. Start the agentic system
+
+The `llama agentic_system` command helps you configure and launch agentic systems. The `llama agentic_system configure` command sets up the configuration file the agentic code expects, and the `llama agentic_system start_app` command streamlines launching.
+
+
+For example, let’s run the included chat app:
+
+```
+llama agentic_system configure
+llama agentic_system start_app chat
+```
+
+For more information run `llama agentic_system --help`.