Add UNISWAP_V4 test coverage to ensure API compliance

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: codebydivine

tests/test_core_types.py

@@ -75,7 +75,7 @@ def test_interval_string_conversion(self):
 
     def test_protocol_string_conversion(self):
         """Test Protocol enum string conversion."""
-        for protocol in [Protocol.UNISWAP_V2, Protocol.UNISWAP_V3]:
+        for protocol in [Protocol.UNISWAP_V2, Protocol.UNISWAP_V3, Protocol.UNISWAP_V4]:
             assert isinstance(str(protocol), str)
             assert str(protocol) == protocol.value