refactor: remove misleading MCPServer type alias in streamable_http_manager

The TYPE_CHECKING import in streamable_http_manager.py was aliasing the
lowlevel `Server` class as `MCPServer`, which is confusing because
`MCPServer` is a separate, higher-level wrapper class defined in
`mcp.server.mcpserver`. This rename removes the alias and uses the
class's actual name `Server` directly.

Author: maxisbey

src/mcp/server/streamable_http_manager.py

@@ -24,7 +24,7 @@
 from mcp.types import INVALID_REQUEST, ErrorData, JSONRPCError
 
 if TYPE_CHECKING:
-    from mcp.server.lowlevel.server import Server as MCPServer
+    from mcp.server.lowlevel.server import Server
 
 logger = logging.getLogger(__name__)
 
@@ -60,7 +60,7 @@ class StreamableHTTPSessionManager:
 
     def __init__(
         self,
-        app: MCPServer[Any, Any],
+        app: Server[Any, Any],
         event_store: EventStore | None = None,
         json_response: bool = False,
         stateless: bool = False,