refactor: remove legacy controller.py and MicMonitor

- Delete engine/controller.py (StreamController - deprecated)
- Delete engine/mic.py (MicMonitor - deprecated)
- Delete tests/test_controller.py (was testing removed legacy code)
- Delete tests/test_mic.py (was testing removed legacy code)
- Update tests/test_emitters.py to test MicSensor instead of MicMonitor
- Clean up pipeline.py introspector to remove StreamController reference
- Update AGENTS.md to reflect architecture changes

tests/test_emitters.py

@@ -58,12 +58,12 @@ class TestProtocolCompliance:
         assert callable(poller.subscribe)
         assert callable(poller.unsubscribe)
 
-    def test_mic_monitor_complies_with_protocol(self):
-        """MicMonitor implements EventEmitter and Startable protocols."""
-        from engine.mic import MicMonitor
+    def test_mic_sensor_complies_with_protocol(self):
+        """MicSensor implements Startable and Stoppable protocols."""
+        from engine.sensors.mic import MicSensor
 
-        monitor = MicMonitor()
-        assert hasattr(monitor, "subscribe")
-        assert hasattr(monitor, "unsubscribe")
-        assert hasattr(monitor, "start")
-        assert hasattr(monitor, "stop")
+        sensor = MicSensor()
+        assert hasattr(sensor, "start")
+        assert hasattr(sensor, "stop")
+        assert callable(sensor.start)
+        assert callable(sensor.stop)