format with clang-format 18.1.0 and fix includes with iwyu 0.22

apps/Coordinator.cpp

apps/EchoClient.cpp

apps/EchoServer.cpp

apps/EchoServerCallback.cpp

apps/FibChildStealing.cpp

apps/WorkerSleepExample.cpp

apps/fsearch/fsearch.cpp

emper/BinaryPrivateSemaphore.cpp

emper/Context.hpp

emper/ContextManager.cpp

emper/CountingPrivateSemaphore.cpp

emper/Dispatcher.cpp

emper/Dispatcher.hpp

emper/Emper.cpp

emper/Emper.hpp

emper/Runtime.cpp

emper/Semaphore.cpp

emper/SynchronizedFiber.hpp

emper/c_emper.cpp

emper/io.hpp