feat: Remove initialize() Method from LlamaStackAsLibrary (#2979)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
This PR removes `init()` from `LlamaStackAsLibrary` 

Currently client.initialize() had to be invoked by user.
To improve dev experience and to avoid runtime errors, this PR init
LlamaStackAsLibrary implicitly upon using the client.
It prevents also multiple init of the same client, while maintaining
backward ccompatibility.

This PR does the following 

- Automatic Initialization: Constructor calls initialize_impl()
automatically.
-  Client is fully initialized after __init__ completes.
- Prevents consecutive initialization after the client has been
successfully initialized.
-  initialize() method still exists but is now a no-op.

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->
fixes https://github.com/meta-llama/llama-stack/issues/2946

---------

Signed-off-by: Mustafa Elbehery <melbeher@redhat.com>

tests/unit/distribution/test_library_client_initialization.py

@@ -5,86 +5,121 @@
 # the root directory of this source tree.
 
 """
-Unit tests for LlamaStackAsLibraryClient initialization error handling.
+Unit tests for LlamaStackAsLibraryClient automatic initialization.
 
-These tests ensure that users get proper error messages when they forget to call
-initialize() on the library client, preventing AttributeError regressions.
+These tests ensure that the library client is automatically initialized
+and ready to use immediately after construction.
 """
 
-import pytest
-
 from llama_stack.core.library_client import (
     AsyncLlamaStackAsLibraryClient,
     LlamaStackAsLibraryClient,
 )
+from llama_stack.core.server.routes import RouteImpls
 
 
-class TestLlamaStackAsLibraryClientInitialization:
-    """Test proper error handling for uninitialized library clients."""
+class TestLlamaStackAsLibraryClientAutoInitialization:
+    """Test automatic initialization of library clients."""
 
-    @pytest.mark.parametrize(
-        "api_call",
-        [
-            lambda client: client.models.list(),
-            lambda client: client.chat.completions.create(model="test", messages=[{"role": "user", "content": "test"}]),
-            lambda client: next(
-                client.chat.completions.create(
-                    model="test", messages=[{"role": "user", "content": "test"}], stream=True
-                )
-            ),
-        ],
-        ids=["models.list", "chat.completions.create", "chat.completions.create_stream"],
-    )
-    def test_sync_client_proper_error_without_initialization(self, api_call):
-        """Test that sync client raises ValueError with helpful message when not initialized."""
-        client = LlamaStackAsLibraryClient("nvidia")
+    def test_sync_client_auto_initialization(self, monkeypatch):
+        """Test that sync client is automatically initialized after construction."""
+        # Mock the stack construction to avoid dependency issues
+        mock_impls = {}
+        mock_route_impls = RouteImpls({})
 
-        with pytest.raises(ValueError) as exc_info:
-            api_call(client)
+        async def mock_construct_stack(config, custom_provider_registry):
+            return mock_impls
 
-        error_msg = str(exc_info.value)
-        assert "Client not initialized" in error_msg
-        assert "Please call initialize() first" in error_msg
+        def mock_initialize_route_impls(impls):
+            return mock_route_impls
 
-    @pytest.mark.parametrize(
-        "api_call",
-        [
-            lambda client: client.models.list(),
-            lambda client: client.chat.completions.create(model="test", messages=[{"role": "user", "content": "test"}]),
-        ],
-        ids=["models.list", "chat.completions.create"],
-    )
-    async def test_async_client_proper_error_without_initialization(self, api_call):
-        """Test that async client raises ValueError with helpful message when not initialized."""
-        client = AsyncLlamaStackAsLibraryClient("nvidia")
+        monkeypatch.setattr("llama_stack.core.library_client.construct_stack", mock_construct_stack)
+        monkeypatch.setattr("llama_stack.core.library_client.initialize_route_impls", mock_initialize_route_impls)
 
-        with pytest.raises(ValueError) as exc_info:
-            await api_call(client)
+        client = LlamaStackAsLibraryClient("ci-tests")
 
-        error_msg = str(exc_info.value)
-        assert "Client not initialized" in error_msg
-        assert "Please call initialize() first" in error_msg
+        assert client.async_client.route_impls is not None
 
-    async def test_async_client_streaming_error_without_initialization(self):
-        """Test that async client streaming raises ValueError with helpful message when not initialized."""
-        client = AsyncLlamaStackAsLibraryClient("nvidia")
+    async def test_async_client_auto_initialization(self, monkeypatch):
+        """Test that async client can be initialized and works properly."""
+        # Mock the stack construction to avoid dependency issues
+        mock_impls = {}
+        mock_route_impls = RouteImpls({})
 
-        with pytest.raises(ValueError) as exc_info:
-            stream = await client.chat.completions.create(
-                model="test", messages=[{"role": "user", "content": "test"}], stream=True
-            )
-            await anext(stream)
+        async def mock_construct_stack(config, custom_provider_registry):
+            return mock_impls
 
-        error_msg = str(exc_info.value)
-        assert "Client not initialized" in error_msg
-        assert "Please call initialize() first" in error_msg
+        def mock_initialize_route_impls(impls):
+            return mock_route_impls
 
-    def test_route_impls_initialized_to_none(self):
-        """Test that route_impls is initialized to None to prevent AttributeError."""
-        # Test sync client
-        sync_client = LlamaStackAsLibraryClient("nvidia")
-        assert sync_client.async_client.route_impls is None
+        monkeypatch.setattr("llama_stack.core.library_client.construct_stack", mock_construct_stack)
+        monkeypatch.setattr("llama_stack.core.library_client.initialize_route_impls", mock_initialize_route_impls)
 
-        # Test async client directly
-        async_client = AsyncLlamaStackAsLibraryClient("nvidia")
-        assert async_client.route_impls is None
+        client = AsyncLlamaStackAsLibraryClient("ci-tests")
+
+        # Initialize the client
+        result = await client.initialize()
+        assert result is True
+        assert client.route_impls is not None
+
+    def test_initialize_method_backward_compatibility(self, monkeypatch):
+        """Test that initialize() method still works for backward compatibility."""
+        # Mock the stack construction to avoid dependency issues
+        mock_impls = {}
+        mock_route_impls = RouteImpls({})
+
+        async def mock_construct_stack(config, custom_provider_registry):
+            return mock_impls
+
+        def mock_initialize_route_impls(impls):
+            return mock_route_impls
+
+        monkeypatch.setattr("llama_stack.core.library_client.construct_stack", mock_construct_stack)
+        monkeypatch.setattr("llama_stack.core.library_client.initialize_route_impls", mock_initialize_route_impls)
+
+        client = LlamaStackAsLibraryClient("ci-tests")
+
+        result = client.initialize()
+        assert result is None
+
+        result2 = client.initialize()
+        assert result2 is None
+
+    async def test_async_initialize_method_idempotent(self, monkeypatch):
+        """Test that async initialize() method can be called multiple times safely."""
+        mock_impls = {}
+        mock_route_impls = RouteImpls({})
+
+        async def mock_construct_stack(config, custom_provider_registry):
+            return mock_impls
+
+        def mock_initialize_route_impls(impls):
+            return mock_route_impls
+
+        monkeypatch.setattr("llama_stack.core.library_client.construct_stack", mock_construct_stack)
+        monkeypatch.setattr("llama_stack.core.library_client.initialize_route_impls", mock_initialize_route_impls)
+
+        client = AsyncLlamaStackAsLibraryClient("ci-tests")
+
+        result1 = await client.initialize()
+        assert result1 is True
+
+        result2 = await client.initialize()
+        assert result2 is True
+
+    def test_route_impls_automatically_set(self, monkeypatch):
+        """Test that route_impls is automatically set during construction."""
+        mock_impls = {}
+        mock_route_impls = RouteImpls({})
+
+        async def mock_construct_stack(config, custom_provider_registry):
+            return mock_impls
+
+        def mock_initialize_route_impls(impls):
+            return mock_route_impls
+
+        monkeypatch.setattr("llama_stack.core.library_client.construct_stack", mock_construct_stack)
+        monkeypatch.setattr("llama_stack.core.library_client.initialize_route_impls", mock_initialize_route_impls)
+
+        sync_client = LlamaStackAsLibraryClient("ci-tests")
+        assert sync_client.async_client.route_impls is not None