fix(connection): reconnect decision closes the failed socket (health_check's documented role) + symmetric backoff-bound test assertion (F3, F5)

custom_components/nvidia_shield/connection.py

@@ -276,7 +276,7 @@ class ShieldConnectionManager:
 
         try:
             if not self.connected and not await self._poller.connect():
-                self._note_failure(backoff)
+                await self._note_failure(backoff)
                 return self._jitter(backoff)
             if self._failures:
                 self._failures = 0
@@ -285,11 +285,11 @@ class ShieldConnectionManager:
             await self._refresh()
             return ADB_POLL_INTERVAL
         except Exception as err:
-            self._note_failure(backoff)
+            await self._note_failure(backoff)
             _LOGGER.debug("Watchdog cycle failed: %s", err)
             return self._jitter(backoff)
 
-    def _note_failure(self, backoff: float) -> None:
+    async def _note_failure(self, backoff: float) -> None:
         """Bookkeep a failed cycle: log sparingly, drop stale store, notify."""
         self._failures += 1
         if self._failures == 1 or self._failures % 6 == 0:
@@ -300,6 +300,13 @@ class ShieldConnectionManager:
             )
         if not self._down_since:
             self._down_since = True
+            # Reconnect decision (health_check's documented role): close the
+            # socket so the next cycle rebuilds it from scratch instead of
+            # trusting shell()'s auto-reconnect on a broken transport.
+            try:
+                await self._poller.disconnect()
+            except Exception:
+                _LOGGER.debug("disconnect during reconnect decision failed", exc_info=True)
             self.store.clear(*ALL_FIELDS)
             self._notify()