src/windows/common/wslutil.h Added new IsVhdFile() helper function declaration src/windows/common/wslutil.cpp Implemented IsVhdFile() to check for both .vhd and .vhdx extensions src/windows/common/WslClient.cpp Removed client-side file extension validation (moved to service) src/windows/service/exe/LxssUserSession.cpp Added service-side validation for VHD export/import operations and dynamic filename handling src/windows/service/exe/WslCoreFilesystem.cpp Simplified assertion to use new IsVhdFile() helper localization/strings/en-US/Resources.resw Updated error messages and help text to clarify .vhd/.vhdx support test/windows/UnitTests.cpp Updated test assertions and added comprehensive ExportImportVhd test test/windows/SimpleTests.cpp Updated test assertions for consistency