Use async_update to set horizontal swing as supported

Reimplement async_update in AtaDeviceClimate (from MelCloudClimate)
so that when the device information is obtained from the cloud, we
check if the device has horizontal vanes to mark SWING_HORIZONTAL_MODE
as a supported feature.

Note that we can't just check for self._device.vane_horizontal in
__init__ since vane_horizontal is only set (or not) after the device
data is fetched from the cloud.

homeassistant/components/melcloud/climate.py

@@ -150,6 +150,14 @@ def __init__(self, device: MelCloudDevice, ata_device: AtaDevice) -> None:
         self._attr_unique_id = f"{self.api.device.serial}-{self.api.device.mac}"
         self._attr_device_info = self.api.device_info
 
+    async def async_update(self) -> None:
+        """Update state from MELCloud."""
+        await super().async_update()
+
+        # We can only check for vane_horizontal once we fetch the device data from the cloud
+        if self._device.vane_horizontal:
+            self._attr_supported_features |= ClimateEntityFeature.SWING_HORIZONTAL_MODE
+
     @property
     def extra_state_attributes(self) -> dict[str, Any] | None:
         """Return the optional state attributes with device specific additions."""
@@ -162,7 +170,6 @@ def extra_state_attributes(self) -> dict[str, Any] | None:
                     ATTR_VANE_HORIZONTAL_POSITIONS: self._device.vane_horizontal_positions,
                 }
             )
-            self._attr_supported_features |= ClimateEntityFeature.SWING_HORIZONTAL_MODE
 
         if vane_vertical := self._device.vane_vertical:
             attr.update(