feat(perf): Implement performance threshold alert system

tests/test_performance_monitor.py

@@ -1,5 +1,6 @@
 import unittest
 import time
+from unittest.mock import MagicMock
 from performance_monitor import PerformanceMonitor
 
 class TestPerformanceMonitor(unittest.TestCase):
@@ -33,5 +34,18 @@ class TestPerformanceMonitor(unittest.TestCase):
         self.assertGreaterEqual(metrics['input_lag_ms'], 20)
         self.assertLess(metrics['input_lag_ms'], 40)
 
+    def test_alerts_triggering(self):
+        mock_callback = MagicMock()
+        self.monitor.alert_callback = mock_callback
+        self.monitor.thresholds['frame_time_ms'] = 5.0  # Low threshold
+        self.monitor._alert_cooldown = 0  # No cooldown for test
+        
+        self.monitor.start_frame()
+        time.sleep(0.01)  # 10ms > 5ms
+        self.monitor.end_frame()
+        
+        mock_callback.assert_called_once()
+        self.assertIn("Frame time high", mock_callback.call_args[0][0])
+
 if __name__ == '__main__':
     unittest.main()