M8-R05: recover WarmteLink ingestion and discovery automatically

app/services/warmtelink_worker.py

@@ -177,7 +177,6 @@ class WarmteLinkWorker:
 
     def _run(self) -> None:
         backoff_index = 0
-        framer = TelegramFramer()
         while not self._stop_event.is_set():
             try:
                 device = self._serial_factory(self.config)
@@ -187,6 +186,11 @@ class WarmteLinkWorker:
                             device.close()
                         return
                     self._serial = device
+                # A disconnect makes any bytes buffered from the previous
+                # descriptor untrustworthy.  In particular, never let a
+                # trailing partial telegram be completed by a newly opened
+                # device.
+                framer = TelegramFramer()
                 while not self._stop_event.is_set():
                     self._expire_discoveries()
                     chunk = device.read(1024)