fix: move CarlaHost to Engine struct and fix TUI plugin dialog access

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

main.c

@@ -97,10 +97,7 @@ int main(int argc, char *argv[]) {
         initial_state.clips[i].read_position = 0;
     }
     
-    // Initialize Carla host in the initial state (before dispatcher starts)
-    carla_init(&initial_state.carla_host, NULL);
-    carla_scan_plugins(&initial_state.carla_host);
-    
+    // Carla host is now initialized in engine_init
     // Initialize dispatcher
     dispatch = dispatcher_init(&initial_state);