feat(v0.2.2): CLI UX improvements with optional test harness

[InitusNovus]

🚀 v0.2.2 Features

CLI UX Improvements

• Short flags: -d (--dbc), -o (--out), -c (--config), -v (--version), -h (--help)
• Better ergonomics: More developer-friendly command-line interface

Optional Test Harness Mode

• New --harness/-t flag: Generate test infrastructure only when needed
• Adaptive Makefile: Dynamic source discovery handles any filename/prefix patterns
• Cross-compatibility: Include header rewriting ensures generated files work together
• Safe operations: Automatic backup of existing files before upgrade

Build System Enhancements

• Dynamic source discovery: Makefile adapts to any generated file patterns (default, sc_, test_, etc.)
• Duplicate handling: Prevents conflicts between utils/registry with different prefixes
• MinGW/Windows support: Cross-platform toolchain override support

CI & Documentation

• Updated CI pipeline: Uses new CLI interface for code generation
• Comprehensive README: CLI flags, harness details, and MinGW build tips
• Progress tracking: Updated GEMINI.md with detailed work records

🔧 Addresses Issues

• Fixes Windows MinGW Makefile generation issue by making test harness optional
• Improves developer experience with intuitive CLI flags and better documentation

✅ Validation

• Build: dotnet build ✅ SUCCESS
• Tests: dotnet test ✅ 16/16 PASSED
• Matrix testing: Default, sc_, test_ prefixes all build successfully
• CLI verification: Short flags working correctly

📝 Changes

• src/Signal.CANdy.CLI/Program.fs: Enhanced CLI with new flags and harness mode
• README.md: Updated documentation with CLI usage and harness details
• infra/ci.yml: Updated CI to use new CLI interface
• GEMINI.md: Progress tracking and work documentation

Ready for merge! 🎉