test(voice): wait on fallback turn completion

tests/test_ai_voice_media_runtime.py

@@ -1387,6 +1387,7 @@ def test_media_runtime_voice_v2_uses_streaming_sidecar_for_partial_and_final_asr
 def test_media_runtime_voice_v2_falls_back_when_streaming_sidecar_is_unavailable():
     registrations: dict[str, MediaRegistration] = {}
     turns: list[str] = []
+    turn_ready = threading.Event()
 
     class _BatchASRProvider(ASRProvider):
         name = "batch-asr"
@@ -1445,6 +1446,7 @@ def test_media_runtime_voice_v2_falls_back_when_streaming_sidecar_is_unavailable
         plan_reply=lambda session_id, text, metadata, kind: None,
         process_turn=lambda session_id, transcript_text, language, barge_in, metadata: (
             turns.append(transcript_text)
+            or turn_ready.set()
             or VoiceAITurnDecisionOut(
                 language=language or "ru",
                 intent="handoff",
@@ -1480,11 +1482,7 @@ def test_media_runtime_voice_v2_falls_back_when_streaming_sidecar_is_unavailable
             writer.write(encode_audio_packet(silence_frame))
         await writer.drain()
 
-        deadline = time.time() + 10.0
-        while time.time() < deadline:
-            if turns:
-                break
-            await asyncio.sleep(0.05)
+        assert await asyncio.to_thread(turn_ready.wait, 10.0)
 
         writer.close()
         await writer.wait_closed()