Business operations API: get_battery_soc/get_household_wattage/get_device_inventory

docs/BATTERY_POC.md

@@ -59,6 +59,21 @@ out = get_battery("...", host="10.100.1.1")
 print(out["value"], out["source"])  # e.g. 78.0 currentBatterySoc
 ```
 
+Business operations (one call per question, on a bound client):
+
+```python
+from franklinwh_agate_client.device_local import LocalDeviceClient
+client = LocalDeviceClient("A03X2516013210060005", host="10.100.1.1",
+                           socket_port=9000)
+client.get_battery_soc()        # charge % (apower, then BMS packs 1-2)
+client.get_household_wattage()  # watts (detail, then load, then EMS math)
+client.get_device_inventory()   # IBG/FHP/BMS serials + versions
+```
+
+`get_*` returns `{"value", "source", "detail", "reply", ...}` with
+`value: None` when nothing answered; transport errors propagate so
+multi-port callers (`get_battery`, `get_power`) can move on.
+
 ## Host probe recipe (run on the machine joined to the device AP)
 
 The agent container cannot reach `10.100.1.x`; run this on the host: