Let a connector's teardown cancellation through too

ConnectorNode.stop cancelled its poll task and then caught CancelledError
around the await — the fourth site of the trap 93e4527 closed elsewhere,
swallowing a cancellation aimed at whoever asked for the teardown. It now
calls the shared Node._cancel_task, which keeps retrieving whatever the
loop raised on its way out, as the old `except (CancelledError, Exception)`
did.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K1moruzue2kTJd3uVisgNk

backend/tests/flow/test_node_teardown.py

@@ -4,17 +4,19 @@ import asyncio
 
 import pytest
 
+from fluksio.flow.connector import ConnectorNode
 from fluksio.flow.nodes import DelayNode
 
 
-def test_stop_cron_lets_the_callers_cancellation_through():
-    async def stubborn() -> None:
-        """A loop whose shutdown does not answer the first cancellation."""
-        try:
-            await asyncio.sleep(3600)
-        except asyncio.CancelledError:
-            await asyncio.sleep(3600)
+async def stubborn() -> None:
+    """A loop whose shutdown does not answer the first cancellation."""
+    try:
+        await asyncio.sleep(3600)
+    except asyncio.CancelledError:
+        await asyncio.sleep(3600)
 
+
+def test_stop_cron_lets_the_callers_cancellation_through():
     async def scenario() -> None:
         node = DelayNode(params={"cron": "* * * * *"})
         node._stop_cron = asyncio.Event()
@@ -29,3 +31,20 @@ def test_stop_cron_lets_the_callers_cancellation_through():
         node._cron_task.cancel()
 
     asyncio.run(scenario())
+
+
+def test_connector_stop_lets_the_callers_cancellation_through():
+    async def scenario() -> None:
+        node = ConnectorNode()
+        node._stop_event = asyncio.Event()
+        node._poll_task = asyncio.create_task(stubborn())
+
+        stopping = asyncio.create_task(node.stop())
+        await asyncio.sleep(0.05)  # let it reach the await on the poll task
+        stopping.cancel()
+        with pytest.raises(asyncio.CancelledError):
+            await stopping
+
+        node._poll_task.cancel()
+
+    asyncio.run(scenario())