Bug/ogc contour and hole share starting point

[NailxSharipov]

Summary

Fix OGC contour traversal to close by starting edge instead of starting node, preventing premature closure when holes share the same node.

Changes

Testing

• cargo test
• cargo fmt
• cargo clippy

Checklist

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

[NailxSharipov]

connected problems #78, #77, #72, #70

[codecov]

Codecov Report

❌ Patch coverage is 68.75000% with 5 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
iOverlay/src/core/extract_ogc.rs	70.00%	3 Missing ⚠️
iOverlay/src/core/extract.rs	66.66%	1 Missing ⚠️
iOverlay/src/vector/extract.rs	66.66%	1 Missing ⚠️

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