feat(voice): run pipeline eyes-free (STT -> Brain -> TTS), defer screen share

Make source/vision optional so the conversation loop runs with no screen
capture. Add Settings.voice() preset and `python -m wsai --voice` demo.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_pipeline.py

@@ -35,6 +35,27 @@ def test_mock_pipeline_runs_and_replies(capsys):
     assert "화면:" in replies[0]
 
 
+def test_voice_only_pipeline_runs_without_eyes():
+    """Eyes-free config (no source/vision) still runs STT -> Brain -> TTS."""
+    replies: list[str] = []
+
+    class CapturingTTS(MockTTS):
+        async def speak(self, reply):
+            replies.append(reply.text)
+
+    pipe = Pipeline(
+        brain=MockBrain(),
+        stt=MockSTT(script=["안녕", "잘 있어"], interval=0.05),
+        tts=CapturingTTS(),
+    )
+
+    asyncio.run(asyncio.wait_for(pipe.run(), timeout=5))
+
+    assert len(replies) == 2, "voice loop did not reply to every utterance"
+    # No eyes → the brain must report it has not seen a screen.
+    assert "아직 화면을 못 읽었어요" in replies[0]
+
+
 def test_history_is_bounded():
     pipe = Pipeline(
         source=MockFrameSource(limit=0),