refactor: improve stress test stability and memory ordering in engine

engine/src/channel.c

@@ -72,8 +72,8 @@ void channel_add(jack_client_t *client, int idx) {
 
 void channel_remove(jack_client_t *client, int idx) {
   (void)client;
-  atomic_store(&channels[idx].active, 0);
-  atomic_fetch_sub(&channel_count, 1);
+  atomic_store_explicit(&channels[idx].active, 0, memory_order_release);
+  atomic_fetch_sub_explicit(&channel_count, 1, memory_order_release);
 }
 
 void channel_add_scene(jack_client_t *client, int idx) {

engine/src/looper.c

@@ -116,9 +116,6 @@ static void exec_command(command_t cmd, jack_client_t *client) {
     // Restore the requested scene (channel_add or add_scene may have reset current_scene)
     atomic_store(&channels[ch].current_scene, requested_scene);
 
-    // Give JACK time to register ports if we created something
-    struct timespec req = {.tv_sec = 0, .tv_nsec = 200000000};
-    nanosleep(&req, NULL);
 
     int sc_idx = atomic_load(&channels[ch].current_scene);
     scene_t *sc_ptr = &channels[ch].scenes[sc_idx];

engine/src/main.c

@@ -52,7 +52,7 @@ int main(int argc, char *argv[]) {
   while (1) {
     looper_process_commands(client);
     {
-      struct timespec ts = {.tv_sec = 0, .tv_nsec = 50000000};
+      struct timespec ts = {.tv_sec = 0, .tv_nsec = 10000000};
       nanosleep(&ts, NULL);
     }
   }