Add lightweight chess engine, analyzer, CLI executable, tests, and README docs

[qqpie4634]

Motivation

• Provide an in-repo chess analysis feature so users can record moves and get engine suggestions without external dependencies.
• Offer a simple command-line tool to run analysis interactively from the terminal.
• Expose the new functionality as part of ChatGPTKit so it can be used by library consumers and the CLI.

Description

• Implement a lightweight chess engine and board model in Sources/ChatGPTKit/Chess/ChessEngine.swift with piece, move, board, legal move generation, evaluation, and basic game state detection.
• Add a ChessGameAnalyzer in Sources/ChatGPTKit/Chess/ChessAnalyzer.swift that runs a Negamax search with alpha-beta and returns ChessAnalysis and MoveReview summaries.
• Add an executable CLI target ChessCLI in Sources/ChessCLI/main.swift and expose it in Package.swift as an executable product and executableTarget that depends on ChatGPTKit.
• Update Sources/ChatGPTKit/ChatGPTKit.swift to import FoundationNetworking to support non-Darwin networking builds and update the README.md with Chinese CLI usage instructions and example code for ChessGameAnalyzer.
• Add unit tests in Tests/ChatGPTKitTests/ChessAnalyzerTests.swift covering initial legal move count, applying a move, and analyzer suggestion behavior.

Testing

• Ran swift test which executed the new test suite ChatGPTKitTests and the three tests testInitialPositionHasTwentyLegalMoves, testApplyMoveE2E4, and testAnalyzerSuggestsMove, all of which passed.
• Performed a swift build of the package to validate the new ChessCLI executable target and library integration, which completed successfully.

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Codex Task