Add author, license, and enhanced model metadata support

[ChinChangYang]

Summary

• Add --author and --license CLI options for setting model metadata
• Enhance model description with architecture info (blocks, channels, source filename)
• Populate Core ML metadata fields: author, license, versionString (model name)
• Add user-defined metadata: model version, precision, meta encoder version

Changes

• Options.hpp: New fields for author, license, source filename, and model architecture
• Converter.cpp: Extract and populate model info from KataGo binary
• CoreMLSerializer.cpp: Enhanced metadata generation with comprehensive model info
• katago2coreml.cpp: CLI argument parsing for --author and --license
• README.md: Documentation for new CLI options and ConversionOptions fields

Example Usage

katago2coreml --author "Your Name" --license MIT model.bin.gz KataGo.mlpackage

Test Plan

• Build and verify CLI accepts new options
• Confirm metadata appears correctly in generated .mlpackage files
• Verify backward compatibility (options are optional)

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