microworld-parallel-sim swallows failures and exits with status 0

[WaterRainting]

Summary

The package-level microworld-parallel-sim entrypoint catches SystemExit from the async simulation runner and then always returns 0.

Affected code

• src/microworld/cli/parallel_simulation.py
• src/microworld/simulation/parallel_simulation_main.py

In parallel_simulation.py, SystemExit is caught and ignored:

except SystemExit:
    pass
...
return 0

But parallel_simulation_main.py intentionally exits with non-zero status for failures, for example:

• missing config file: sys.exit(1)
• invalid topology cluster config: sys.exit(2)

Why this matters

Shell scripts, CI, and parent orchestration code can treat a failed simulation as successful when using the package script entrypoint.

Expected behavior

microworld-parallel-sim should preserve the non-zero exit code from the underlying runner.

Suggested fix

Capture SystemExit as exc and return int(exc.code or 0), or let the exception propagate after cleanup.