Fix: drop W=H constraint and regenerate gpt5 baseline for problem 0

[YanagiOrigami]

• Remove the stray "W=H" condition from the bounding-box description in statement.txt; W and H are independent per the rest of the problem.
• Regenerate examples/gpt5.cpp with gpt-5 against the corrected statement so the baseline reflects the non-square rectangle objective.

Summary

Please read CONTRIBUTING.md before submitting.

Type of Change

• New research problem
• New algorithmic problem
• New Frontier-CS 2.0 problem
• Bug fix
• Documentation update
• Other:

Testing

Checklist

• Code follows the project structure and conventions
• Self-review completed
• Documentation updated (if applicable)

CI Validation (for new problems)

When adding new problems, CI will automatically validate that your reference solution achieves score > 0.

• Algorithmic problems: Include reference.cpp in your problem directory
• Research problems: Include reference.py (or reference.cpp if language: cpp in config.yaml)
• 2.0 problems: Include reference.py unless the problem config declares another language

[joyemang33]

LGTM! this will close #119