Pool has no shutdown story — items it created leak when the app stops

Pool has no shutdown story — items it created leak when the app stops: a task in MiMo-V2.6-RL-oss: Agentic RL Environments (MiMo RL release). I'm following the channel pooling pattern from the docs (docs/source/examples/pooling.py): one Pool produces AMQP connections, a second Pool produces…