test(voice): harden streaming fallback scenario

tests/test_ai_voice_media_runtime.py

@@ -1474,13 +1474,13 @@ def test_media_runtime_voice_v2_falls_back_when_streaming_sidecar_is_unavailable
 
         speech_frame = (1000).to_bytes(2, "little", signed=True) * 160
         silence_frame = b"\x00\x00" * 160
-        for _ in range(2):
+        for _ in range(4):
             writer.write(encode_audio_packet(speech_frame))
-        for _ in range(2):
+        for _ in range(4):
             writer.write(encode_audio_packet(silence_frame))
         await writer.drain()
 
-        deadline = time.time() + 5.0
+        deadline = time.time() + 10.0
         while time.time() < deadline:
             if turns:
                 break