fix(gateway): re-send rate caps when the hub's online message arrives

_check_rate_caps() only noticed the hub was offline if a run() cycle landed
while it was. A reboot after a firmware update is quicker than the gap
between cycles, so the offline state was never seen and unchanged caps were
not sent again - leaving a hub that had just gained the command, or lost its
stored caps, without them.

The online-message handler now clears what was sent on any online/offline
transition.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: CI

apps/predbat/gateway.py

@@ -773,6 +773,10 @@ async def _handle_message(self, message):
                 self._gateway_online = payload == "1"
                 if self._gateway_online != was_online:
                     self.log(f"Info: GatewayMQTT: Gateway is {'online' if self._gateway_online else 'offline'}")
+                    # A hub that has been away may be on new firmware or have lost its stored
+                    # rate caps, so send them again. Done here, not only in _check_rate_caps():
+                    # a reboot is quicker than the gap between two run() cycles.
+                    self._rate_caps_sent.clear()
                     self.dashboard_item(
                         f"binary_sensor.{self.prefix}_gateway_online",
                         self._gateway_online,

apps/predbat/tests/test_gateway.py

@@ -3876,6 +3876,36 @@ def test_held_while_hub_offline_and_sent_again_when_it_returns(self):
         self._run(gw._check_rate_caps())
         assert len(gw._published) == 2
 
+    def test_hub_restart_between_cycles_is_told_again(self):
+        """A hub that goes offline and returns between two run() cycles is still re-sent its caps.
+
+        A reboot after a firmware update takes well under the 60 seconds between cycles, so
+        _check_rate_caps() never sees the hub offline. The online message itself must clear
+        what was sent.
+        """
+        from unittest.mock import MagicMock
+
+        gw = self._make_gateway()
+        gw._inverter_slot_serials = ["CH2330G098"]
+        gw.base.inverters = [self._inverter(0, 3000, 3600)]
+        gw.prefix = "predbat"
+        gw.topic_status = "predbat/devices/pbgw_test/status"
+        gw.topic_online = "predbat/devices/pbgw_test/online"
+        gw.dashboard_item = MagicMock()
+        gw._error_count = 0
+        self._run(gw._check_rate_caps())
+        assert len(gw._published) == 1
+
+        for payload in (b"0", b"1"):
+            message = MagicMock()
+            message.topic = gw.topic_online
+            message.payload = payload
+            self._run(gw._handle_message(message))
+
+        self._run(gw._check_rate_caps())
+        assert len(gw._published) == 2
+        assert gw._error_count == 0
+
     def test_nothing_sent_before_auto_config(self):
         """Until auto-config has bound slots to serials there is nothing to key a cap on."""
         gw = self._make_gateway(auto_configured=False)