fix(core): a turn cut by shutdown keeps running_turn for recover

src/beaver_gateway/core/conversations.py

@@ -825,6 +825,7 @@ class Conversations:
                 item_origin=item_origin,
             )
             stop = "error"
+            cut = False
             try:
                 events = backend.complete(
                     agent=self._claude_agent(conv.agent_name),
@@ -841,9 +842,12 @@ class Conversations:
                 async for event in events:
                     yield event
                 stop = "interrupted" if capture.interrupted else "end_turn"
+            except asyncio.CancelledError:
+                cut = True
+                raise
             finally:
                 runner.turn_id = None
-                await self._mark_done(conv, capture)
+                await self._mark_done(conv, capture, cut=cut)
                 self._bus.publish(
                     "turn.end",
                     conversation_id=conv.external_id,
@@ -1173,9 +1177,14 @@ class Conversations:
 
         await self._update(conv, apply)
 
-    async def _mark_done(self, conv: Conversation, capture: TurnCapture) -> None:
+    async def _mark_done(
+        self, conv: Conversation, capture: TurnCapture, *, cut: bool = False
+    ) -> None:
+        """Close the turn; a cancelled one keeps ``running_turn`` for ``recover``."""
+
         async def apply(row: Conversation) -> None:
-            row.running_turn = None
+            if not cut:
+                row.running_turn = None
             row.last_activity_at = datetime.now(UTC)
             if capture.session_id is not None:
                 row.session_id = capture.session_id