Inconsistant Behaviour When Trying to Terminate MLGym Process

### Describe the bug

When users try to terminate an MLGym process prematurely, there's a chance that the process will refuse to exit.

### Steps/commands/code to Reproduce

```
git clone git@github.com:facebookresearch/MLGym.git
cd MLGym
conda create -y -n mlgym python=3.11
conda activate mlgym
pip install -e .

podman machine init
podman machine start
export DOCKER_HOST=unix://$(podman machine inspect --format '{{.ConnectionInfo.PodmanSocket.Path}}')

podman pull aigym/mlgym-agent:latest

python run.py \
--container_type podman \
--task_config_path tasks/battleOfSexes.yaml \
--model litellm:claude-3-5-sonnet-20240620 \
--per_instance_cost_limit 4.00 \
--agent_config_path configs/agents/default.yaml \
--temp 1 \
--gpus 0 \
--max_steps 50 \
--aliases_file ./docker/aliases.sh

Ctrl + c
```

### Error message/results

The process sometimes refuses to exit.

### System Information

Current MLGym

### Checklist

- [x] I'm running with the latest docker container/on the latest development version (i.e., I ran `git pull`))
- [x] I have copied the full command/code that I ran (as text, not as screenshot!)
- [x] If applicable: I have copied the **full** log file/error message that was the result (as text, not as screenshot!)
- [x] I have enclosed code/log messages in triple backticks ([docs](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#quoting-code)) and clicked "Preview" to make sure it's displayed correctly.

Start with run.py and reproduce the command in the issue using Podman, then interrupt it with Ctrl+C while observing whether the main process and its container exit. Trace the process and container shutdown path from that entry point; done means a premature interrupt reliably terminates the launched work and returns control to the shell.

Written by the indexing model from the issue text.