Fire onChapter on chapter boundaries; M returns to menu via onMenu

The menu state machine advances via onChapter events when a video crosses a
chapter marker, which we never emitted - so the menu never opened naturally.
Track chapter boundaries from the playlist markers and fire onChapter. Also
change M to invoke the onMenu dispatcher (returns to the menu video) rather
than drawing menu items directly.

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

@@ -80,6 +80,8 @@ 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]);
             }

ui/src/main/java/dev/quoije/umd/ui/PlayerApp.java

@@ -70,6 +70,7 @@ public final class PlayerApp extends Application {
 
     private volatile VsmxInterpreter menuInterpreter;
     private volatile VsmxBaseObject mmActivate;
+    private volatile VsmxNativeObject controllerObject;
 
     @Override
     public void start(Stage stage) {
@@ -146,11 +147,14 @@ public final class PlayerApp extends Application {
     }
 
     private void openMenuDirectly() {
-        VsmxBaseObject fn = mmActivate;
         VsmxInterpreter interpreter = menuInterpreter;
-        if (fn instanceof VsmxFunction function && interpreter != null) {
+        VsmxNativeObject c = controllerObject;
-            System.err.println("[debug] opening menu directly");
+        if (interpreter != null && c != null) {
-            interpreter.interpretFunction(function, null, new VsmxBaseObject[0]);
+            VsmxBaseObject callback = c.getPropertyValue("onMenu");
+            if (callback instanceof VsmxFunction function) {
+                System.err.println("[debug] returning to menu");
+                interpreter.interpretFunction(function, null, new VsmxBaseObject[0]);
+            }
         }
     }
 
@@ -181,7 +185,7 @@ public final class PlayerApp extends Application {
                                       int audioFlag, int subtitleNumber, int subtitleFlag) {
                     Playlist.Stream stream = playlist.streamForPlayListNumber(playListNumber);
                     if (stream != null) {
-                        startPlayback(isoPath, stream.name(), playListNumber);
+                        startPlayback(isoPath, stream, playListNumber);
                     }
                 }
 
@@ -209,13 +213,15 @@ public final class PlayerApp extends Application {
             moviePlayer = (MoviePlayer) movieplayer.getObject();
             menuInterpreter = interpreter;
             mmActivate = globals.getPropertyValue("mm_activate");
+            this.controllerObject = controllerObject;
             controller.callCallback(interpreter, "onAutoPlay", null);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 
-    private void startPlayback(String isoPath, String streamName, int playListNumber) {
+    private void startPlayback(String isoPath, Playlist.Stream stream, int playListNumber) {
+        String streamName = stream.name();
         Thread player = new Thread(() -> {
             try (UmdIsoReader iso = new UmdIsoReader(Path.of(isoPath));
                  PlaybackEngine engine = PlaybackEngine.open(iso, streamName, 0)) {
@@ -232,11 +238,22 @@ public final class PlayerApp extends Application {
                 long baseNanos = clockStartNanos;
 
                 PlaybackEngine.VideoFrame frame;
+                int lastChapter = -2;
                 while ((frame = engine.nextVideoFrame()) != null) {
                     if (skipRequested) {
                         skipRequested = false;
                         break;
                     }
+                    int chapter = stream.getChapterNumber(frame.pts());
+                    if (chapter != lastChapter) {
+                        if (lastChapter != -2) {
+                            MoviePlayer mp = moviePlayer;
+                            if (mp != null) {
+                                mp.onChapter(chapter + 1);
+                            }
+                        }
+                        lastChapter = chapter;
+                    }
                     int index = videoBufferIndex++ & 1;
                     int[] argb = argbBuffers[index];
                     int pixelCount = frame.width() * frame.height();