fix: guard transient controls and verify timeline endpoints

artemis/drivers/base.py

@@ -99,6 +99,10 @@ class BaseDeviceDriver(ABC):
         """
         ...
 
+    async def get_ui_elements(self) -> list[dict]:
+        """Read the current hierarchy; drivers may avoid a full screenshot here."""
+        return (await self.get_screen_data()).ui_elements or []
+
     @abstractmethod
     async def tap(
         self,