feat(config_flow): standalone setup — androidtv entity optional with no_state_source validation, entry data omits the field for standalone entries, sensor tolerates its absence; migration keeps v1 field / v2 absence valid (P3-1a,d)

custom_components/nvidia_shield/sensor.py

@@ -73,7 +73,7 @@ class NvidiaShieldCurrentAppSensor(NvidiaShieldSensorBase):
 
     def __init__(self, hass: HomeAssistant, entry: ConfigEntry) -> None:
         super().__init__(hass, entry)
-        self._androidtv_entity = entry.data[CONF_ANDROIDTV_ENTITY]
+        self._androidtv_entity = entry.data.get(CONF_ANDROIDTV_ENTITY, "")
         self._attr_unique_id = f"{DOMAIN}_{entry.entry_id}_current_app"
 
     def _manager(self) -> ShieldConnectionManager | None: