Add cleanup task registration and execution in ScriptApi

src/main/java/net/jstom/script/ScriptApi.java

@@ -17,6 +17,7 @@ import java.lang.reflect.Modifier;
 public class ScriptApi {
     private final List<EventNode<Event>> registeredNodes = new ArrayList<>();
     private final List<Entity> trackedEntities = new ArrayList<>();
+    private final List<Value> cleanupTasks = new ArrayList<>();
     private static final Map<String, EntityType> entityTypes = new HashMap<>();
 
     static {
@@ -32,6 +33,18 @@ public class ScriptApi {
         }
     }
 
+    /**
+     * Registers a cleanup task.
+     * Usage in JS: server.onCleanup(() => { timer.cancel(); });
+     */
+    public void onCleanup(Value callback) {
+        if (callback.canExecute()) {
+            synchronized (cleanupTasks) {
+                cleanupTasks.add(callback);
+            }
+        }
+    }
+
     /**
      * Registers an event listener from JavaScript.
      * Usage in JS: server.on('net.minestom.server.event.player.PlayerLoginEvent', (event) => { ... });
@@ -82,6 +95,19 @@ public class ScriptApi {
     }
 
     public void cleanup() {
+        System.out.println("[JStom] Running " + cleanupTasks.size() + " cleanup tasks...");
+        synchronized (cleanupTasks) {
+            for (Value task : cleanupTasks) {
+                try {
+                    task.executeVoid();
+                } catch (Exception e) {
+                    System.err.println("[JStom] Error in cleanup task:");
+                    e.printStackTrace();
+                }
+            }
+            cleanupTasks.clear();
+        }
+
         System.out.println("[JStom] Cleaning up " + registeredNodes.size() + " event nodes...");
         for (var node : registeredNodes) {
             MinecraftServer.getGlobalEventHandler().removeChild(node);