🧪 Add tests for validate_weapons.rb

[hahwul]

🎯 What: Missing tests for scripts/validate_weapons.rb have been implemented.
📊 Coverage: A new suite of Minitests added in test/test_validate_weapons.rb. The test covers seven distinct scenarios, simulating missing/empty fields, invalid YAML formatting, and correct records, executing via temporary subdirectories and mocked config files.
✨ Result: A significant testing gap is now addressed. This ensures that any refactoring of the YAML validation logic is fully covered, capturing edge cases correctly before committing new code.

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PR created automatically by Jules for task 16901216635599438305 started by @hahwul

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