fix: catch OSError on sounddevice import in voice_mode.py

Same PortAudio fix as tts_tool.py — sounddevice raises OSError
when the native library is missing on CI runners.

tools/voice_mode.py

@@ -31,7 +31,7 @@ try:
     import numpy as np
 
     _HAS_AUDIO = True
-except ImportError:
+except (ImportError, OSError):
     sd = None  # type: ignore[assignment]
     np = None  # type: ignore[assignment]
     _HAS_AUDIO = False