feat: add dual module support (CommonJS + ESM)

[scottlovegrove]

Summary

• Add dual module support to enable compatibility with both CommonJS and ES Module projects
• Implement TypeScript configurations for separate CommonJS and ESM builds
• Create automated post-build script to fix ESM imports with required .js extensions
• Update package.json with proper exports field and dual entry points
• Modernize Jest configuration for ESM compatibility

Changes Made

New Files

• tsconfig.cjs.json - CommonJS build configuration
• tsconfig.esm.json - ESM build configuration
• scripts/fix-esm-imports.cjs - Post-build script to add .js extensions for ESM compliance

Modified Files

• package.json - Added dual module support with exports field and updated build scripts
• jest.config.js - Converted to ESM format with modern ts-jest configuration

Build Output Structure

dist/
├── cjs/              # CommonJS output
│   ├── package.json  # Marks directory as CommonJS
│   └── ...
├── esm/              # ESM output (with .js extensions)
│   └── ...
└── types/            # TypeScript declarations
    └── ...

Benefits

• Backward compatibility - Existing CommonJS projects continue working unchanged
• ESM support - Modern projects can use native ES modules
• NestJS compatibility - Resolves ES module resolution issues
• Tree-shaking - ESM builds enable better bundling optimizations
• Future-proof - Aligns with Node.js ecosystem direction

Test Plan

• All existing tests pass (262 tests)
• Build process generates correct dual output structure
• CommonJS imports work correctly
• ESM imports work correctly
• Module instantiation works for both formats
• ESM import fixing adds .js extensions properly

🤖 Generated with Claude Code