Load the event stream fix after it's no longer a dataclass

[enyst]

End-user friendly description of the problem this fixes or functionality that this introduces

• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below
  Fix loading the stream from the file store.

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We just removed the @ dataclass annotation from EventStream. There is actually another detail about dataclass: it was calling __post_init__ implicitly. Without it, it will never be called and the stream is not restored.

This PR fixes it.

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Link of any specific issues this addresses

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:ab5d4c9-nikolaik   --name openhands-app-ab5d4c9   docker.all-hands.dev/all-hands-ai/openhands:ab5d4c9

[rbren]

oops how bad was this break?

[enyst]

oops how bad was this break?

Well, for a New Year's Eve, pretty tame! ❤️