Optional aGate address on the API (home-LAN direct connect)

AgateClient takes address= default; attach_local accepts
address/host/gateway_ip per call with join control. An explicit
address skips the SoftAP radio join by default (join=True forces
it). derive_hotspot_credentials and join_device_hotspot accept a
gateway_ip override. battery/power host defaults now use
DEVICE_GATEWAY_IP. Verified live at 192.168.1.142:9000.

franklinwh_agate_client/battery.py

@@ -20,7 +20,7 @@ from typing import Any, Dict, List, Optional, Tuple
 
 from .device_local import LocalDeviceClient
 from .protocol import CommunicationCmd
-from .wifi import derive_hotspot_credentials
+from .wifi import DEVICE_GATEWAY_IP, derive_hotspot_credentials
 
 log = logging.getLogger(__name__)
 
@@ -144,7 +144,7 @@ def _is_empty_pack(reply: Dict[str, Any], result: Dict[str, Any]) -> bool:
 
 def get_battery(
     sn: str,
-    host: str = "10.100.1.1",
+    host: str = DEVICE_GATEWAY_IP,
     ports: Tuple[int, ...] = SOCKET_PORT_CANDIDATES,
     key_radix: int = 16,
     timeout: float = 5.0,
@@ -197,7 +197,7 @@ PROBE_VARIANTS: Tuple[Tuple[str, CommunicationCmd, Any], ...] = (
 
 def probe_device(
     sn: str,
-    host: str = "10.100.1.1",
+    host: str = DEVICE_GATEWAY_IP,
     ports: Tuple[int, ...] = SOCKET_PORT_CANDIDATES,
     key_radix: int = 16,
     timeout: float = 5.0,
@@ -262,7 +262,7 @@ _MQTT_CONNECT = bytes.fromhex("101200044d5154540402003c000670726f62653031")
 
 def probe_transport(
     sn: str,
-    host: str = "10.100.1.1",
+    host: str = DEVICE_GATEWAY_IP,
     ports: Tuple[int, ...] = (9000,),
     key_radix: int = 16,
     timeout: float = 5.0,
@@ -327,7 +327,7 @@ def main(argv: Optional[List[str]] = None) -> int:
         description="Read aGate battery percentage over the device SoftAP socket."
     )
     parser.add_argument("--sn", required=True, help="20-char device serial")
-    parser.add_argument("--host", default="10.100.1.1", help="aGate gateway IP")
+    parser.add_argument("--host", default=DEVICE_GATEWAY_IP, help="aGate gateway IP")
     parser.add_argument(
         "--ports", default=",".join(map(str, SOCKET_PORT_CANDIDATES)),
         help="comma-separated socket ports to probe",