fix: vector subtraction bug

[Pluto417-Qing]

📘 Pull Request Template – PhysicsHub

Thank you for contributing to PhysicsHub!
Please complete the sections below to help us review your pull request efficiently.

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🔍 Description

fix Vectors Subtraction Bug, see the image below to see the effect.

Closes #ISSUE_ID (if applicable)
#87

✅ Checklist

Before requesting a review, please ensure that you have:

• Verified that the project builds and runs locally (npm run dev)
• Ensured no ESLint or TypeScript warnings/errors remain
• Updated documentation, comments, or in-code explanations where needed
• Verified responsiveness across devices (desktop, tablet, mobile)
• Followed the CONTRIBUTING.md guidelines

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🎨 Visual Changes (if UI-related)

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📂 Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 📝 Documentation update
• ♻️ Refactor / code quality improvement
• 🎨 UI/UX enhancement
• 🔒 Security improvement

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🧩 Additional Notes for Reviewers

[physicshub]

Hey, thank you so much for this, as I said also to others contributors unfortunatly I can't review PRs until this weekend, due Erasmus project at school.
I will review that soon!

[physicshub]

Thank you so much for contributing!