Summary

Creates a new header include/kcenon/thread/concepts/thread_concepts.h that:

• Integrates C++20 Concepts from common_system
• Provides thread-specific concepts (JobType, JobCallable, Duration, etc.)
• Re-exports common_system concepts when available

Parent Issue

Part of #271

Tasks

• Create concepts/ directory
• Implement thread_concepts.h with both common_system integration and standalone fallbacks
• Add comprehensive documentation

Related Files

• include/kcenon/thread/concepts/thread_concepts.h