feat: normalize user agent with other do clients

Author: bbatha

src/gradient/_base_client.py

@@ -671,7 +671,7 @@ def _validate_headers(
 
     @property
     def user_agent(self) -> str:
-        return f"{self.__class__.__name__}/Python {self._version}"
+        return f"{self.__class__.__name__}/Python/{self._version}"
 
     @property
     def base_url(self) -> URL: