Use static self-registration for action queue and variable setup

Removes explicit setup calls from the plugin core. Each module now
registers its own save/load/cleanup steps via a static initializer,
decoupling them from InitSceneSwitcher and SwitcherData.

lib/queue/action-queue.cpp

@@ -12,20 +12,16 @@ std::deque<std::shared_ptr<Item>> &GetActionQueues()
 	return queues;
 }
 
-void RegisterActionQueueTab();
-
-void SetupActionQueues()
+static bool setup()
 {
-	static bool done = false;
-	if (done) {
-		return;
-	}
 	AddSaveStep(SaveActionQueues);
 	AddLoadStep(LoadActionQueues);
-	RegisterActionQueueTab();
-	done = true;
+	AddPluginCleanupStep([]() { queues.clear(); });
+	return true;
 }
 
+static bool setupDone = setup();
+
 ActionQueue::ActionQueue() : Item()
 {
 	_lastEmpty = std::chrono::high_resolution_clock::now();