fix: resolve circular import and ruff lint issues

- utils.py imported from mcp.client.auth (package __init__) instead of
  mcp.client.auth.exceptions directly, creating a circular dependency that
  forced authlib_adapter to be imported last in __init__.py (violating
  import order). Fix by importing directly from the exceptions module.
- Reorder __init__.py imports alphabetically (ruff I001)
- Remove unused MagicMock import from test file (ruff F401)
- Remove extra blank line in test imports (ruff E303)

Author: harsh543

src/mcp/client/auth/__init__.py

@@ -3,13 +3,13 @@
 Implements authorization code flow with PKCE and automatic token refresh.
 """
 
+from mcp.client.auth.authlib_adapter import AuthlibAdapterConfig, AuthlibOAuthAdapter
 from mcp.client.auth.exceptions import OAuthFlowError, OAuthRegistrationError, OAuthTokenError
 from mcp.client.auth.oauth2 import (
     OAuthClientProvider,
     PKCEParameters,
     TokenStorage,
 )
-from mcp.client.auth.authlib_adapter import AuthlibAdapterConfig, AuthlibOAuthAdapter
 
 __all__ = [
     "AuthlibAdapterConfig",

src/mcp/client/auth/utils.py

@@ -4,7 +4,7 @@
 from httpx import Request, Response
 from pydantic import AnyUrl, ValidationError
 
-from mcp.client.auth import OAuthRegistrationError, OAuthTokenError
+from mcp.client.auth.exceptions import OAuthRegistrationError, OAuthTokenError
 from mcp.client.streamable_http import MCP_PROTOCOL_VERSION
 from mcp.shared.auth import (
     OAuthClientInformationFull,

tests/client/auth/test_authlib_adapter.py

@@ -10,7 +10,7 @@
 from __future__ import annotations
 
 from typing import Any
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import AsyncMock, patch
 
 import httpx
 import pytest
@@ -19,7 +19,6 @@
 from mcp.client.auth.exceptions import OAuthFlowError
 from mcp.shared.auth import OAuthToken
 
-
 # ---------------------------------------------------------------------------
 # Helpers / fixtures
 # ---------------------------------------------------------------------------