Add close() to Transport protocol for resource cleanup parity

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: adamtheturtle

src/vws/transports.py

@@ -18,6 +18,10 @@ class Transport(Protocol):
     returns a ``Response``.
     """
 
+    def close(self) -> None:
+        """Close the transport and release resources."""
+        ...  # pylint: disable=unnecessary-ellipsis
+
     def __call__(
         self,
         *,
@@ -51,6 +55,13 @@ class RequestsTransport:
     This is the default transport.
     """
 
+    def close(self) -> None:
+        """Close the transport.
+
+        This is a no-op for ``RequestsTransport`` as it does not
+        hold persistent connections.
+        """
+
     def __call__(
         self,
         *,