fix(cli): llama model prompt-format (#1481)

Summary:

+ llama model prompt-format -m Llama3.2-11B-Vision-Instruct
Traceback (most recent call last):
  File "/tmp/tmp.gCwyyCcjoA/.venv/bin/llama", line 10, in <module>
    sys.exit(main())
File
"/tmp/tmp.gCwyyCcjoA/.venv/lib/python3.10/site-packages/llama_stack/cli/llama.py",
line 50, in main
    parser.run(args)
File
"/tmp/tmp.gCwyyCcjoA/.venv/lib/python3.10/site-packages/llama_stack/cli/llama.py",
line 44, in run
    args.func(args)
File
"/tmp/tmp.gCwyyCcjoA/.venv/lib/python3.10/site-packages/llama_stack/cli/model/prompt_format.py",
line 59, in _run_model_template_cmd
    if args.list:
AttributeError: 'Namespace' object has no attribute 'list'

Test Plan:
llama model prompt-format -m Llama3.2-11B-Vision-Instruct

llama_stack/cli/model/prompt_format.py

@@ -13,7 +13,7 @@ from llama_stack.cli.subcommand import Subcommand
 from llama_stack.cli.table import print_table
 from llama_stack.models.llama.datatypes import CoreModelId, ModelFamily, is_multimodal, model_family
 
-ROOT_DIR = Path(__file__).parent.parent
+ROOT_DIR = Path(__file__).parent.parent.parent
 
 
 class ModelPromptFormat(Subcommand):
@@ -44,6 +44,12 @@ class ModelPromptFormat(Subcommand):
             default="llama3_1",
             help="Model Family (llama3_1, llama3_X, etc.)",
         )
+        self.parser.add_argument(
+            "-l",
+            "--list",
+            action="store_true",
+            help="List all available models",
+        )
 
     def _run_model_template_cmd(self, args: argparse.Namespace) -> None:
         import importlib.resources