fix: add internal lookup for hidden compiler words

Co-authored-by: aider (openrouter/moonshotai/kimi-k2.6) <aider@aider.chat>

forth_dict.c

@@ -26,3 +26,10 @@ Word* lookup_word(const char* name) {
     }
     return NULL;
 }
+
+Word* lookup_word_internal(const char* name) {
+    for (Word* w = dict_head; w != NULL; w = w->prev) {
+        if (strcmp(w->name, name) == 0) return w;
+    }
+    return NULL;
+}