fix(backends,conversations,telegram,ui): a background subagent reports back as its own turn

tests/test_claude_sdk_backend.py

@@ -86,6 +86,7 @@ class FakeClient:
         self.prompts: list[str] = []
         self.connected = False
         self.session_id = options.resume or "fresh-session"
+        self.asked = asyncio.Event()
         FakeClient.instances.append(self)
 
     async def connect(self) -> None:
@@ -93,6 +94,17 @@ class FakeClient:
 
     async def query(self, prompt: str) -> None:
         self.prompts.append(prompt)
+        self.asked.set()
+
+    async def receive_messages(self):
+        served = 0
+        while True:
+            while len(self.prompts) <= served:
+                self.asked.clear()
+                await self.asked.wait()
+            served += 1
+            async for message in self.receive_response():
+                yield message
 
     async def interrupt(self) -> None:
         self.interrupted = True