wip: fix existing todos

Co-authored-by: Github CoPilot

include/threadlist.h

@@ -22,6 +22,7 @@
 // doubly linked list implementation for managing threads
 typedef struct pthread_list_node {
     pthread_t thread;
+    pthread_mutex_t mutex;
     struct pthread_list_node* previous;
     struct pthread_list_node* next;
 } pthread_list_node;