fix: promoting moves are animated

[antonryoung02]

Description

I added utils.getPromotionUpdates and utils.pawnPromotesAtSquares to identify promoting moves.

In the animation useEffect I added a condition where the promotion is animated only if positionUpdates doesn't have any pieces to animate and promotionUpdates has one piece to animate. I added these constraints to simplify the problem, because the main benefit of the fix is to animate when only the promotion move is being played or undone. In other cases it can be hard to verify if the promotion actually happened or how you should handle conflicts with positionUpdates.

Fixes #220

Type of change

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• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

• Verified the animation happens when the engine promotes in Storybook > Options API > animationDurationInMs

I didn't write any unit tests for my logic because I didn't see a test suite to add them to. Let me know if I'm misunderstanding storybook!

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Additional context

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Project	Deployment	Preview	Comments	Updated (UTC)
react-chessboard	Ready	Preview	Comment	Nov 12, 2025 11:40pm

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