Fix: Gymnasium compliance and corner points detection bug

[faustoallegrini]

This PR introduces two key fixes to improve compliance and correctness:

1. Gymnasium API compliance

   • Explicitly handle seed parameter in reset(seed=...) for reproducible initialization
   • Pass custom attributes via options in reset(..., options=...) instead of positional arguments
   • Ensure step(...) returns the truncated flag along with (obs, reward, terminated, truncated, info)

2. Corner points detection bug

   • Corrected logic error in the corner detection algorithm that caused incomplete detection
   • Ensured all valid corner points are properly identified

[floriankagerer]

Hello faustoallegrini,
many thanks for your contribution to this repository.

I'm afraid that I need more time to carefully review your changes.
What I can say from a first look:

1. Thanks for detecting a bug in the corner point detection. I'd really appreciate if you also add tests for the corner point detection (instead of print, please use logger.debug).
2. Instead of using {} as default argument in the reset methods, please use None.
3. Thanks for showing improvements regarding the Gymnasium compliance. To be honest, I just updated the import and did not take care of the methods, which were designed for gym.
4. Regarding the updates of the preview items and selectable items: I agree with your argument, that there should not be a difference in the logic. However, my plan is to refactor this logic in two dedicated modules, so I'd prefer to keep it as it is now and to update the logic when implementing these modules.

Thanks again for your contribution.
I am looking forward to hearing again from you.

Best regards,
Florian

[faustoallegrini]

Hello Florian,
Thank you for your feedback.
I created a fictitious, simplified order named “2orders-mikp” with a container size of 15×10 to provide a clearer visualization of the CPs. Running this order using the “LowestArea” heuristic helps cover several edge cases in the CP algorithm logic.
Additionally, I implemented a function to plot both the heightmap and the corresponding corner points. You can test this by running the script demo_gym_palenv.py.

Best regards,
Fausto