fix: ignore stale callbacks from rescheduled timers

- Add generation counters to SmartCondition and EventSensor timers.
- Preserve pending changes and the retention period when timers are restarted.
- Silently cancel timers that have already expired.
- Add regression tests for stale callbacks and expiry during cancellation.

unit_tests/test_event_sensor.py

@@ -0,0 +1,79 @@
+"""An expired timer queued before reactivation must not end the new window."""
+import ast
+from pathlib import Path
+from types import SimpleNamespace
+import unittest
+from unittest.mock import Mock
+
+from test_continuous_condition import FakeScheduler
+
+source = Path(__file__).resolve().parents[1] / 'virtualsensors.py'
+node = next(node for node in ast.parse(source.read_text()).body
+            if isinstance(node, ast.ClassDef) and node.name == 'EventSensor')
+namespace = {'VirtualSensorBase': object, 'EventHandler': Mock()}
+exec(compile(ast.Module(body=[node], type_ignores=[]), str(source), 'exec'), namespace)
+EventSensor = namespace['EventSensor']
+
+
+class EventSensorTests(unittest.TestCase):
+    def setUp(self):
+        self.scheduler = FakeScheduler()
+        self.state = 'off'
+        entity = Mock()
+        entity.exists.return_value = True
+        entity.set_state.side_effect = lambda *, state: setattr(self, 'state', state)
+        self.sensor = EventSensor()
+        self.sensor.ad_api = SimpleNamespace(
+            get_entity=lambda name: entity,
+            run_in=self.scheduler.run_in,
+            cancel_timer=self.scheduler.cancel_timer,
+        )
+        self.sensor.sensor_name = 'binary_sensor.red_shelly_home'
+        self.sensor.yaml_block = {'retain_time': 120}
+        self.sensor.initialize()
+
+    def activate(self):
+        self.sensor.on_activation_event('signal_strength', {}, {})
+        return self.sensor.cb_handle
+
+    def test_current_expiry_turns_sensor_off(self):
+        handle = self.activate()
+        self.assertEqual(self.state, 'on')
+        self.scheduler.expire(handle)()
+        self.assertEqual(self.state, 'off')
+        self.assertIsNone(self.sensor.cb_handle)
+
+    def test_reactivation_cancels_running_timer(self):
+        old = self.activate()
+        current = self.activate()
+        self.assertNotIn(old, self.scheduler.timers)
+        self.assertIn(current, self.scheduler.timers)
+        self.assertEqual(self.state, 'on')
+        self.assertEqual(self.scheduler.warnings, [])
+
+    def test_queued_expiry_preserves_reactivated_sensor_and_timer(self):
+        queued = self.scheduler.expire(self.activate())
+        current = self.activate()
+        queued()
+        self.assertEqual(self.state, 'on')
+        self.assertEqual(self.sensor.cb_handle, current)
+        self.assertEqual(self.scheduler.warnings, [])
+        self.scheduler.expire(current)()
+        self.assertEqual(self.state, 'off')
+        self.assertIsNone(self.sensor.cb_handle)
+
+    def test_multiple_queued_expiries_cannot_end_latest_window(self):
+        first = self.scheduler.expire(self.activate())
+        second = self.scheduler.expire(self.activate())
+        current = self.activate()
+        second()
+        first()
+        self.assertEqual(self.state, 'on')
+        self.assertEqual(self.sensor.cb_handle, current)
+        self.assertEqual(self.scheduler.warnings, [])
+        self.scheduler.expire(current)()
+        self.assertEqual(self.state, 'off')
+
+
+if __name__ == '__main__':
+    unittest.main()