refactor: make interpreter portable with static pools and I/O hooks

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

forth_dict.c

@@ -1,11 +1,7 @@
 #include "forth.h"
 
 Word* add_primitive(const char* name, void (*code)(Word*), uint8_t flags) {
-    Word* w = malloc(sizeof(Word));
-    if (!w) {
-        fprintf(stderr, "Out of memory\n");
-        exit(1);
-    }
+    Word* w = forth_alloc_word();
     w->prev = dict_head;
     dict_head = w;