fix(zoom): fix Stack to Volume Fusion and Viewport zoom preservation

[sedghi]

fixes #1996

This pull request includes significant changes to the stackToVolumeFusion example, improvements to the BaseVolumeViewport class, and updates to the testing configuration and test cases. The most important changes are detailed below.

New Example Implementation:

• packages/core/examples/stackToVolumeFusion/index.ts: Added a new example demonstrating stack to volume fusion and volume with labelmap segmentation. This includes initializing the rendering engine, creating viewports, and setting up volumes and segmentations.

Rendering Engine Enhancements:

• packages/core/src/RenderingEngine/BaseVolumeViewport.ts: Updated the BaseVolumeViewport class to handle cases where volumeId is undefined and to correctly set the camera focal point and position based on the image position and normal direction. [1] [2] [3]
• packages/core/src/RenderingEngine/Viewport.ts: Modified the Viewport class to use the default actor's bounds for computing visible prop bounds, improving the accuracy of the camera's focal point.

Testing Configuration and Test Cases:

• playwright.config.ts: Increased the number of workers in CI from 4 to 12 to speed up test execution.
• tests/stackToVolumeFusion.spec.ts: Added a new test case to verify the display of a single DICOM series in a volume viewport and take a screenshot for visual verification.
• tests/utils/screenShotPaths.ts: Updated the screenshot paths utility to include paths for the new stackToVolumeFusion example.

CC @wayfarer3130

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tests/stackToVolumeFusion.spec.ts:17

• [nitpick] Consider using a dynamic waiting mechanism (e.g., waitForSelector) instead of a fixed timeout to improve test reliability.

await page.waitForTimeout(2000);

[wayfarer3130]

Can you add the new example to the examples list?

[sedghi]

I didn't really plan to use it for showcasing; I think the example page is already pretty crowded. My intention was to use it for end-to-end tests.