Open menu naturally via chapter events; M returns to menu; debounce M

The menu state machine advances from the menu-intro state to the menu state
only when the menu video crosses its chapter-2 marker (onChapter). Fire
onChapter from the video loop as PTS crosses playlist markers. Also route the
M key through the onMenu dispatcher so it returns to the menu video/title
(not just drawing menu items), and debounce the key against auto-repeat.

core/src/main/java/dev/quoije/umd/rco/vsmx/objects/MoviePlayer.java

@@ -80,8 +80,6 @@ public class MoviePlayer extends BaseNativeObject {
 
         if (!previousMenuMode && this.menuMode) {
             VsmxBaseObject callback = controller.getPropertyValue("onMenu");
-            System.err.println("[menu] onMenu fires, callback=" + callback
-                    + " (" + (callback == null ? "null" : callback.getClass().getSimpleName()) + ")");
             if (callback instanceof VsmxFunction function) {
                 interpreter.interpretFunction(function, null, new VsmxBaseObject[0]);
             }