Make aggregate return an AsyncIterator, other clean up

tests/test_ivr_navigation.py

@@ -10,6 +10,7 @@ from unittest.mock import AsyncMock
 from pipecat.audio.vad.vad_analyzer import VADParams
 from pipecat.extensions.ivr.ivr_navigator import IVRProcessor
 from pipecat.frames.frames import (
+    LLMFullResponseEndFrame,
     LLMMessagesUpdateFrame,
     LLMTextFrame,
     OutputDTMFUrgentFrame,
@@ -334,10 +335,12 @@ class TestIVRNavigation(unittest.IsolatedAsyncioTestCase):
 
         frames_to_send = [
             LLMTextFrame(text="Hello, I'm trying to reach billing."),
+            LLMFullResponseEndFrame(),
         ]
 
         expected_down_frames = [
             LLMTextFrame,  # Should pass through unchanged
+            LLMFullResponseEndFrame,
         ]
 
         expected_up_frames = [