Thread Management (join, detach, jthread)

Creating a std::thread is the easy part. The harder part is what happens after, because every running thread has to be either waited for or explicitly cut loose before its std::thread object is destroyed. Getting that step wrong calls std::terminate. This chapter covers join(), detach(), joinable(), why exceptions make manual cleanup fragile, how RAII wrappers fix the problem, and how std::jthread (C++20) bakes the safe pattern into the standard library along with cooperative cancellation through std::stop_token.