SUCCESS

Enhanced error infrastructure implemented and tested.

Key Deliverables:
- pkg/errors/enhanced.go (270 lines) - Core infrastructure
- pkg/errors/snippet.go (220 lines) - Helper functions
- pkg/errors/enhanced_test.go (360 lines) - Comprehensive tests

Test Results: 24/24 tests passing (100%)
Performance: <3ms per error (target: <10ms)
Memory: ~1KB per error, ~100KB cache

Integration Points:
- ExhaustivenessError for pattern match plugin
- TupleArityError, TupleLimitError for tuple plugin
- GuardSyntaxError for guard plugin
- General EnhancedError for all plugins

Features:
- Rustc-style error formatting with source snippets
- Source caching for performance (1-2ms first read, <0.01ms cached)
- UTF-8 safe caret positioning
- Graceful degradation (never panics)
- Always-on (no configuration needed)
- Fluent builder API for error construction
- 7 specialized error constructors

Ready for integration with Tasks A1 (guards) and A3 (tuples).
