refactor: IWYU updates

src/core/include/mp-units/compat_macros.h

@@ -90,6 +90,7 @@
 
 #ifndef MP_UNITS_IN_MODULE_INTERFACE
 
+// IWYU pragma: begin_exports
 #if MP_UNITS_USE_FMTLIB
 MP_UNITS_DIAGNOSTIC_PUSH
 MP_UNITS_DIAGNOSTIC_IGNORE_UNREACHABLE
@@ -99,5 +100,6 @@ MP_UNITS_DIAGNOSTIC_POP
 #else
 #include <format>
 #endif
+// IWYU pragma: end_exports
 
 #endif