feat(events): Add EventEmitter and instrument ai_client.py

tests/test_api_events.py

@@ -0,0 +1,20 @@
+
+import pytest
+from unittest.mock import MagicMock
+import ai_client
+
+def test_ai_client_event_emitter_exists():
+    # This should fail initially because 'events' won't exist on ai_client
+    assert hasattr(ai_client, 'events')
+    assert ai_client.events is not None
+
+def test_event_emission():
+    # We'll expect these event names based on the spec
+    mock_callback = MagicMock()
+    ai_client.events.on("request_start", mock_callback)
+    
+    # Trigger something that should emit the event (once implemented)
+    # For now, we just test the emitter itself if we were to call it manually
+    ai_client.events.emit("request_start", payload={"model": "test"})
+    
+    mock_callback.assert_called_once_with(payload={"model": "test"})