add vertical divider, window_drag_area doc example tests

[OwenMcDonnell]

Description

Docs example tests and images for vertical divider, window_drag_area.

Summary by Sourcery

Add automated example tests and update control examples and documentation to integrate golden-image screenshots for VerticalDivider and WindowDragArea

New Features:

• Add integration tests with screenshot comparisons for VerticalDivider and WindowDragArea examples

Enhancements:

• Update example scripts to use explicit dimension settings and guard main execution with if __name__ == '__main__'
• Adjust documentation to reference centralized test-images and include illustrative captions in class summaries

Documentation:

• Point example_images paths to generated golden images directory
• Enhance class_summary invocations to display example images with captions

Tests:

• Include golden-image tests for example controls to validate rendering under LIGHT theme
• Add parameterized tests to capture full-page screenshots of the basic examples

[sourcery-ai]

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