Add corner‑case tests for vector simplify

[mikhailofff]

Summary

#29

Changes

New tests have been added covering various scenarios for simplifying vector contours:

1. Duplicate points
2. Very short segments ("tiny segments")
3. Sequences of collinear segments ("collinear runs")
4. Zero-area paths

Testing

• cargo test
• cargo fmt
• cargo clippy

Checklist

• Added tests for new behavior or bug fixes
• Updated docs/examples if needed

[NailxSharipov]

Thanks for putting these tests together - great work!
One note: the contours in the examples aren't valid closed chains.

For a contour we need consecutive edges:

[a0, b0], [a1, b1], [a2, b2], [a3, b3], ... [an, bn]

where

b0 == a1, b1 == a2, ... bn == a0

Could you update the test data so each contour is a proper closed loop?

[codecov]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

ℹ️ You can also turn on project coverage checks and project coverage reporting on Pull Request comment

Thanks for integrating Codecov - We've got you covered ☂️