feat: Add comprehensive May library improvement analysis and implementation PRD

This commit introduces three comprehensive analysis documents and an implementation PRD:

## Documents Added:

### AI_USAGE_GUIDE.md
- Complete API reference and usage patterns for AI systems
- Safety rules, configuration examples, and best practices
- Common pitfalls, performance considerations, and debugging guides
- Integration patterns with other libraries and frameworks

### MAY_IMPROVEMENT_ANALYSIS.md
- Analysis of current unsafe spawn requirements and safety issues
- Concrete solutions for TLS detection and stack overflow prevention
- Type-safe spawn APIs with CoroutineSafe trait implementation
- 8-month roadmap for achieving 90%+ safe API coverage

### MAY_MESSAGE_PASSING_IMPROVEMENTS.md
- Comprehensive analysis of current channel implementations (SPSC, MPSC, MPMC)
- Advanced channel variants: lock-free MPMC with work stealing, priority channels
- Reactive extensions API with map/filter/batch operators
- Performance optimizations: NUMA awareness, zero-copy operations, batching
- Enhanced select operations and comprehensive monitoring infrastructure

### tasks/tasks.md - Implementation PRD
- 24-month implementation plan across 6 major phases
- Expected outcomes: 10-50% performance gains, 90% safe API coverage
- Technical architecture specifications and success metrics
- Risk mitigation strategies and backward compatibility guarantees

## Key Improvements Proposed:

### Safety Enhancements:
- Compile-time TLS detection via proc macros
- Runtime TLS guards and stack overflow prevention
- Type-safe spawn APIs eliminating unsafe requirements
- Enhanced builder patterns for safe configuration

### Performance Optimizations:
- Lock-free MPMC channels with 2-5x performance improvement
- Priority-based message passing with strict ordering
- NUMA-aware design for multi-socket systems
- Zero-copy operations and batched processing

### Developer Experience:
- Reactive programming patterns (map, filter, batch, debounce)
- Comprehensive monitoring and debugging infrastructure
- Enhanced select operations (weighted, priority, conditional)
- Builder patterns for type-safe channel configuration

### Ecosystem Integration:
- Development tools (linter, safety monitor, benchmarks)
- Monitoring integrations (Prometheus, OpenTelemetry)
- Documentation and tutorial series
- Community adoption strategies

This work positions May as the leading Rust coroutine library for high-performance
applications while maintaining 100% backward compatibility throughout the transition.

Co-authored-by: AI Assistant <ai@microscaler.com>

Author: casibbald