feat(renderer): Implement getPieceIndexAt Method

[TKanX]

Summary:

Introduces a new public method, getPieceIndexAt(x, y), to the Renderer. This method provides a direct way to get a piece's index from canvas coordinates, enabling developers to build custom interactions like tooltips or hover effects without being tied to the built-in event system. It effectively serves as the public-facing reverse operation to getPieceCoordinates, enhancing the library's flexibility.

Changes:

• Added Public Method:

  • Implemented renderer.getPieceIndexAt(x, y) to retrieve a piece index from canvas coordinates. This method leverages the internal hitmap for efficient lookups, returning -1 if no piece is found.

• API Documentation:

  • Added comprehensive documentation for the new getPieceIndexAt method in API.md, including a description, parameter details, and a clear usage example.
  • Updated the Table of Contents to include the new method.

[Copilot]

Pull Request Overview

This PR introduces a new public method getPieceIndexAt(x, y) to the Renderer class that allows developers to retrieve a piece's index from canvas coordinates. This enables custom interactions like tooltips and hover effects without relying on the built-in event system.

• Added getPieceIndexAt method to the Renderer class
• Updated API documentation with comprehensive details and usage examples
• Updated table of contents to include the new method

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/renderer.js	Implements the new getPieceIndexAt method using internal hitmap lookup
docs/API.md	Adds complete documentation for the new method and updates TOC structure

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