Document dlfcn shim source basis

core/wasm_shims/dlfcn.cc

@@ -2,6 +2,8 @@
 
 #include <cstring>
 
+// LinuxCNC source basis: src/emc/rs274ngc/interp_base.cc uses dlopen(),
+// dlsym(), dlerror(), RTLD_GLOBAL, and RTLD_NOW for native interpreter loading.
 namespace {
 
 thread_local char last_error[128] = "dynamic loading is unavailable in wasm-safe probe";
@@ -27,4 +29,3 @@ int dlclose(void *) {
 }
 
 } // extern "C"
-