BUG: MonteCarlo returns normally after KeyboardInterrupt

[ting-hong-shieh]

Describe the bug

MonteCarlo.simulate() returns normally after the user interrupts a run.

In serial mode, __run_in_serial() catches KeyboardInterrupt, prints that files were saved, appends the current input record to the error file, and then returns. In parallel mode, __run_in_parallel() catches KeyboardInterrupt, signals and joins the workers, but only re-raises non-keyboard exceptions.

The public simulate() method then calls __terminate_simulation() and returns as if the requested number of simulations completed. Callers cannot distinguish a partial run from a successful one without inspecting the output files.

To reproduce

Start a serial or parallel Monte Carlo run and interrupt it with Ctrl-C. At cb6106a717207dd8fc2dfe1446d80ff75022f21b, control returns normally after the cleanup message instead of propagating KeyboardInterrupt.

Expected behavior

RocketPy should preserve completed rows and stop or join active workers, then re-raise the original KeyboardInterrupt. This lets command-line callers return the conventional interrupted status and lets Python callers handle a partial run explicitly.

The saved files should remain usable with the documented append=True continuation path.

Proposed fix

Keep the current cleanup and file-preservation behavior in both execution modes, but re-raise after cleanup. Add serial and parallel regression tests that verify:

• completed rows remain readable;
• workers are signalled and joined;
• __terminate_simulation() does not convert the interrupted run into success;
• the caller receives KeyboardInterrupt.

The relevant control flow is also being changed by #1054, so implementation should follow that pull request rather than introducing a conflicting parallel-run rewrite.

Environment

• Base SHA: cb6106a717207dd8fc2dfe1446d80ff75022f21b
• RocketPy 1.13.0
• Python 3.12.6
• NumPy 2.5.2
• SciPy 1.18.0
• pytest 9.1.1
• macOS 26.5.2, arm64

[ting-hong-shieh]

I reproduced the interrupt behavior while measuring the slow-test coverage at cb6106a717207dd8fc2dfe1446d80ff75022f21b.

Command:

$ pytest tests --runslow -m slow --cov=rocketpy --cov-append --cov-report=

During test_monte_carlo_simulate[True], sending Ctrl-C did not terminate pytest. The Monte Carlo case returned control to the test, was marked as failed, and pytest continued into the next slow case. A second Ctrl-C was handled the same way; I ultimately had to send SIGQUIT to terminate the run.

This is consistent with both simulation paths catching KeyboardInterrupt and returning normally after cleanup. It also makes an apparently stalled Monte Carlo run difficult to stop from a test runner or terminal.

Environment:

• macOS 26.5.2, arm64
• Python 3.12.6
• RocketPy 1.13.0
• NumPy 2.5.2
• SciPy 1.18.0
• pytest 9.1.1

The intended regression test should assert that cleanup and file persistence finish, then that the original KeyboardInterrupt escapes simulate() in both serial and parallel modes. I will keep the implementation behind #1054 so it does not duplicate or conflict with that process-handling work.