test(gateway): accept language/source args in gateway transcribe_audio stubs

The pre_transcription hook threads (path, language, source) through
gateway voice transcription; three sibling telegram-voice tests pinned
the old single-arg call shape.

tests/gateway/test_telegram_audio_vs_voice.py

@@ -74,7 +74,7 @@ async def test_voice_message_still_transcribed():
             history=[],
         )
 
-    mock_transcribe.assert_called_once_with("/tmp/voice.ogg")
+    mock_transcribe.assert_called_once_with("/tmp/voice.ogg", None, "gateway")
     # The transcript passes through as a plain quoted line — no "voice message"
     # meta-commentary in the LLM-visible prompt.
     assert "hello world" in result

tests/gateway/test_telegram_voice_v0_regressions.py

@@ -163,7 +163,7 @@ async def test_pending_voice_interrupt_reuses_transcript_and_echo():
     assert interrupt_text == '"hello once"'
     assert drain_text == interrupt_text
     assert drain_transcripts == interrupt_transcripts == ["hello once"]
-    mock_transcribe.assert_called_once_with("/tmp/telegram-voice.ogg")
+    mock_transcribe.assert_called_once_with("/tmp/telegram-voice.ogg", None, "gateway")
     adapter.send.assert_awaited_once_with(
         "12345",
         '🎙️ "hello once"',
@@ -216,7 +216,7 @@ async def test_monitor_to_drain_transcribes_and_echoes_pending_voice_once(
 
     assert result["final_response"] == "follow-up complete"
     assert _PendingVoiceAgent.messages == ["initial turn", '"hello once"']
-    mock_transcribe.assert_called_once_with("/tmp/telegram-pending-voice.ogg")
+    mock_transcribe.assert_called_once_with("/tmp/telegram-pending-voice.ogg", None, "gateway")
     assert adapter.sent == [("12345", '🎙️ "hello once"', None)]