feat(cli): add llama-models CLI for standalone model management (#403)

This adds a complete command-line interface for managing Llama models independently of llama-stack. Users can now install llama-models and use the 'llama-model' command to list, download, describe, and verify models from both Meta and HuggingFace.

The CLI provides model discovery (list/describe), downloading from Meta's signed URLs or HuggingFace repos, checksum verification for Meta downloads, and local model management (list downloaded, remove). All model SKU definitions and download logic are now self-contained in this package.

This separation allows partners and users to manage models without requiring the full llama-stack installation, improving modularity and reducing dependency bloat.

Test Plan:
- Verified `llama-model --help` shows all subcommands
- Tested `llama-model model list` displays model table
- Tested `llama-model model describe -m Llama3.2-1B` shows model details
- Confirmed all imports resolve correctly
- Pre-commit hooks pass (license headers, ruff, formatting)

Author: ashwinb

README.md

@@ -39,15 +39,31 @@ To download the model weights and tokenizer:
 1. Visit the [Meta Llama website](https://llama.meta.com/llama-downloads/).
 2. Read and accept the license.
 3. Once your request is approved you will receive a signed URL via email.
-4. Install the [Llama CLI](https://github.com/meta-llama/llama-stack): `pip install llama-stack`. (**<-- Start Here if you have received an email already.**)
-5. Run `llama model list` to show the latest available models and determine the model ID you wish to download. **NOTE**:
-If you want older versions of models, run `llama model list --show-all` to show all the available Llama models.
+4. Install the Llama Models CLI: `pip install llama-models`. (**<-- Start Here if you have received an email already.**)
+5. Run `llama-model list` to show the latest available models and determine the model ID you wish to download. **NOTE**:
+If you want older versions of models, run `llama-model list --show-all` to show all the available Llama models.
 
-6. Run: `llama download --source meta --model-id CHOSEN_MODEL_ID`
+6. Run: `llama-model download --source meta --model-id CHOSEN_MODEL_ID`
 7. Pass the URL provided when prompted to start the download.
 
 Remember that the links expire after 24 hours and a certain amount of downloads. You can always re-request a link if you start seeing errors such as `403: Forbidden`.
 
+### CLI Commands Reference
+
+Once installed, the `llama-model` CLI provides the following commands:
+
+```bash
+llama-model list              # List available models
+llama-model list --show-all   # List all models (including older versions)
+llama-model describe -m MODEL_ID     # Show detailed information about a model
+llama-model download          # Download models from Meta or Hugging Face
+llama-model verify-download   # Verify integrity of downloaded models
+llama-model remove -m MODEL_ID       # Remove a downloaded model
+llama-model prompt-format -m MODEL_ID  # Show the prompt format for a model
+```
+
+For detailed help on any command, run `llama-model COMMAND --help`.
+
 ## Running the models
 
 In order to run the models, you will need to install dependencies after checking out the repository.

models/cli/__init__.py

@@ -0,0 +1,6 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# top-level folder for each specific model found within the models/ directory at
+# the top-level of this source tree.

models/cli/describe.py

@@ -0,0 +1,71 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# top-level folder for each specific model found within the models/ directory at
+# the top-level of this source tree.
+
+import argparse
+import json
+
+from llama_models.cli.subcommand import Subcommand
+from llama_models.cli.table import print_table
+from llama_models.sku_list import resolve_model
+
+
+class Describe(Subcommand):
+    """Show details about a model"""
+
+    def __init__(self, subparsers: argparse._SubParsersAction):
+        super().__init__()
+        self.parser = subparsers.add_parser(
+            "describe",
+            prog="llama-model describe",
+            description="Show details about a llama model",
+            formatter_class=argparse.RawTextHelpFormatter,
+        )
+        self._add_arguments()
+        self.parser.set_defaults(func=self._run_model_describe_cmd)
+
+    def _add_arguments(self):
+        self.parser.add_argument(
+            "-m",
+            "--model-id",
+            type=str,
+            required=True,
+            help="See `llama-model list` or `llama-model list --show-all` for the list of available models",
+        )
+
+    def _run_model_describe_cmd(self, args: argparse.Namespace) -> None:
+        from llama_models.cli.safety_models import prompt_guard_model_sku_map
+
+        prompt_guard_model_map = prompt_guard_model_sku_map()
+        if args.model_id in prompt_guard_model_map.keys():
+            model = prompt_guard_model_map[args.model_id]
+        else:
+            model = resolve_model(args.model_id)
+
+        if model is None:
+            self.parser.error(
+                f"Model {args.model_id} not found; try 'llama-model list' for a list of available models."
+            )
+            return
+
+        headers = [
+            "Model",
+            model.descriptor(),
+        ]
+
+        rows = [
+            ("Hugging Face ID", model.huggingface_repo or "<Not Available>"),
+            ("Description", model.description),
+            ("Context Length", f"{model.max_seq_length // 1024}K tokens"),
+            ("Weights format", model.quantization_format.value),
+            ("Model params.json", json.dumps(model.arch_args, indent=4)),
+        ]
+
+        print_table(
+            rows,
+            headers,
+            separate_rows=True,
+        )