feat: Expand C++17 kernel subsystem with OOP device framework, containers, and benchmark engine

- Implement modern freestanding C++17 containers (Vector<T>, UniquePtr<T>, String) in kernel/cpp/cpp_containers.hpp
- Implement object-oriented Device driver model (Device, BlockDevice, CharDevice, VirtualRamDiskDevice, VirtualNullDevice, VirtualZeroDevice, DeviceManager) in kernel/cpp/cpp_device.hpp and kernel/cpp/cpp_device.cpp
- Add C++ kernel performance microbenchmark suite in kernel/cpp/cpp_bench.cpp
- Export C-FFI bridges and add cross-architecture fallbacks in kernel/cpp/cpp_fallback.c and include/kernel/cpp_kernel.h
- Add LazyBox applets: 'cppdevs' and 'cppbench'
- Update README.md documentation and command matrix

kernel/cpp/cxx_runtime.cpp

@@ -29,6 +29,10 @@ extern "C" {
         return 0; // Kernel runs indefinitely until shutdown
     }
 
+    int atexit(void (*/*func*/)(void)) {
+        return 0;
+    }
+
     void __cxa_pure_virtual(void) {
         panic("C++ Pure Virtual Function Called");
     }