Add comprehensive JSDoc documentation to TypeScript definition files - #24

The JavaScript package's TypeScript definition files (types.d.ts and index.d.ts) were missing comprehensive JSDoc documentation, limiting IntelliSense support and developer experience for users of the opt-in generic typing features.

What Changed

Enhanced types.d.ts with comprehensive documentation:

• Added detailed JSDoc comments for all public APIs (Context, MutableContext, Link, Chain, Middleware classes)
• Documented generic type parameters (TInput, TOutput) with usage examples
• Explained type evolution patterns using insertAs<TNew>() method for clean transformations
• Added performance characteristics documentation (immutability, deep copying, runtime overhead)
• Included error handling patterns and best practices
• Provided extensive mixed typed/untyped usage examples throughout all classes

Enhanced index.d.ts with package overview:

• Added comprehensive package documentation and usage patterns
• Documented import/export patterns for CommonJS and ES modules
• Included TypeScript and JavaScript compatibility guidance

Key Documentation Features

Type Evolution Examples:

interface UserInput { name: string; email: string; }
interface UserValidated extends UserInput { isValid: boolean; }

const inputCtx = new Context<UserInput>({ name: 'Alice', email: 'alice@example.com' });
// Clean type evolution without casting
const validatedCtx = inputCtx.insertAs<UserValidated>('isValid', true);

Performance Guidance:

• Documented zero runtime overhead for typing (same storage as Record<string, any>)
• Explained immutability costs and when to use MutableContext for performance-critical sections
• Provided timing guidance for bulk operations

Error Handling Patterns:

• Comprehensive error handling documentation for typed contexts
• Link validation patterns and error transformation examples
• Chain error recovery strategies with type safety

IntelliSense Improvements

The enhanced documentation now provides:

• Rich hover information for all classes and methods
• Parameter guidance with type information and examples
• Usage examples directly in IDE tooltips
• Error handling patterns and common pitfalls
• Performance guidance for production usage

Backward Compatibility

All documentation additions maintain full backward compatibility:

• ✅ No changes to runtime behavior
• ✅ Support for both typed and untyped usage patterns
• ✅ Works with CommonJS and ES modules
• ✅ TypeScript and JavaScript compatibility preserved

The TypeScript definitions now provide production-grade IntelliSense support with comprehensive documentation that matches the quality of other language implementations while maintaining CodeUChain's philosophy of universal accessibility.

Fixes #19.

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