fix: copy AppState via memcpy to avoid stack overflow

Co-authored-by: aider (deepseek/deepseek-coder) <aider@aider.chat>

dispatcher.c

@@ -594,7 +594,7 @@ static void* dispatcher_thread_func(void *arg) {
 // ============================================================
 
 DispatchFn dispatcher_init(AppState *initial_state) {
-    dispatcher.state = *initial_state;
+    memcpy(&dispatcher.state, initial_state, sizeof(AppState));
     atomic_store(&dispatcher.running, false);
     atomic_store(&dispatcher.write_index, 0);
     atomic_store(&dispatcher.read_index, 0);