fix(pipeline): cancel sibling loops on failure (TaskGroup, no close-during-use)

Pipeline.run() used asyncio.gather, so if one loop raised, the failing
coroutine propagated while the sibling loops kept running detached; aclose()
in the finally then closed a source/stt out from under a still-live loop.
Switch to asyncio.TaskGroup so a failing loop cancels+awaits the siblings
before teardown. Add a regression test asserting an error in the conversation
loop cancels the perception loop and still closes every source.

tests/test_pipeline.py

@@ -3,6 +3,8 @@ into the brain's replies."""
 
 import asyncio
 
+import pytest
+
 from wsai.backends.mock import (
     MockBrain,
     MockFrameSource,
@@ -10,6 +12,7 @@ from wsai.backends.mock import (
     MockTTS,
     MockVision,
 )
+from wsai.interfaces import Frame
 from wsai.pipeline import Pipeline
 
 
@@ -56,6 +59,44 @@ def test_voice_only_pipeline_runs_without_eyes():
     assert "아직 화면을 못 읽었어요" in replies[0]
 
 
+def test_error_in_one_loop_cancels_siblings_and_closes():
+    """If the conversation loop raises, the perception loop must be cancelled
+    (not left running detached) and every source must still be closed — i.e. no
+    close-during-use and no orphaned task."""
+    closed = {"source": False, "stt": False}
+
+    class ForeverSource:
+        async def frames(self):
+            while True:
+                await asyncio.sleep(0.01)
+                yield Frame(data=b"", width=1, height=1, ts=0.0)
+
+        async def aclose(self):
+            closed["source"] = True
+
+    class BoomSTT(MockSTT):
+        async def aclose(self):
+            closed["stt"] = True
+
+    class BoomBrain(MockBrain):
+        async def respond(self, user_text, screen, history):
+            raise RuntimeError("boom")
+
+    pipe = Pipeline(
+        source=ForeverSource(),
+        vision=MockVision(),
+        brain=BoomBrain(),
+        stt=BoomSTT(script=["hi"], interval=0.01),
+        tts=MockTTS(),
+    )
+
+    with pytest.raises(BaseException):  # TaskGroup raises an ExceptionGroup
+        asyncio.run(asyncio.wait_for(pipe.run(), timeout=5))
+
+    assert closed["source"] is True, "perception source was not closed (orphaned loop)"
+    assert closed["stt"] is True, "stt was not closed"
+
+
 def test_history_is_bounded():
     pipe = Pipeline(
         source=MockFrameSource(limit=0),