chore: Stack server no longer depends on llama-stack-client (#4094)

This dependency has been bothering folks for a long time (cc @leseb). We
really needed it due to "library client" which is primarily used for our
tests and is not a part of the Stack server. Anyone who needs to use the
library client can certainly install `llama-stack-client` in their
environment to make that work.

Updated the notebook references to install `llama-stack-client`
additionally when setting things up.

src/llama_stack/core/library_client.py

@@ -18,14 +18,21 @@ from typing import Any, TypeVar, Union, get_args, get_origin
 import httpx
 import yaml
 from fastapi import Response as FastAPIResponse
-from llama_stack_client import (
-    NOT_GIVEN,
-    APIResponse,
-    AsyncAPIResponse,
-    AsyncLlamaStackClient,
-    AsyncStream,
-    LlamaStackClient,
-)
+
+try:
+    from llama_stack_client import (
+        NOT_GIVEN,
+        APIResponse,
+        AsyncAPIResponse,
+        AsyncLlamaStackClient,
+        AsyncStream,
+        LlamaStackClient,
+    )
+except ImportError as e:
+    raise ImportError(
+        "llama-stack-client is not installed. Please install it with `uv pip install llama-stack[client]`."
+    ) from e
+
 from pydantic import BaseModel, TypeAdapter
 from rich.console import Console
 from termcolor import cprint