test: add comprehensive SPolygon unit tests for PR #45

Add tests to restore code coverage above 50% threshold:
- SPolygonTest: 14 tests for creation, translate, resize, clone, edge cases
- ShapeFactory: Updated contract tests to include SPolygon
- SVGDraftmanTest: 4 tests for SVG polygon rendering
- HTMLDraftmanTest: 4 tests for HTML/CSS polygon rendering
- ShapeDraftmanTest: 2 tests for Graphics2D polygon drawing

All tests use reflection to work with SPolygon class.
Fixes coverage failure on PR #45 (Issue #38).

.gitignore

@@ -33,3 +33,4 @@ dependency-reduced-pom.xml
 buildNumber.properties
 .mvn/timing.properties
 .mvn/wrapper/maven-wrapper.jar
+new-shapes.wiki/