Play feature under the menu; add mpv path; simplify VLC launch

Root causes found this session (all player-side, disc is valid -- bd_info
validates it and mpv plays the ISO's feature directly):

- Plain 'vlc <iso>' can't run ANY BD-J: system Java is 26, and libbluray's BD-J
  needs a JVM where System.setSecurityManager() works (<=21). run-vlc.sh pins
  mise Temurin 8, which is why it gets a menu at all.
- The BD-J VFS-cache 'error creating /tmp/libbluray-bdj-cache' flood is
  libbluray's SecurityManager.canWrite() denying the cache root while an Xlet
  context is active. Fixed by pointing TMPDIR at LIBBLURAY_CACHE_ROOT (buda
  root), which canWrite() allows unconditionally.
- Menu->playback failed with 'blurayReleaseVout: subpicture channel exists':
  VLC botches the background->playlist transition for an idle BD-J menu. Now the
  Xlet starts the feature immediately and draws the menu on top, so VLC stays in
  normal playing mode; MAIN FEATURE just hides the menu, any key brings it back,
  and the feature loops.

Also: drop the redundant tools/vlc-plugins swap (system VLC already ships the
bluray plugin), and add scripts/run-mpv.sh to play the feature with no BD-J/JVM
at all. Vendored the SDK helloworld sample for reference.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vendor/bdj-sdk/samples/helloworld/.gitignore

@@ -0,0 +1,6 @@
+*~
+*.class
+discdir
+META-INF
+*.iso
+

vendor/bdj-sdk/samples/helloworld/Makefile

@@ -0,0 +1,80 @@
+#   Copyright (C) 2022 John Törnblom
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING. If not see
+# <http://www.gnu.org/licenses/>.
+
+
+DISC_LABEL := helloworld
+
+#
+# Host tools
+#
+MAKEFILE_DIR := $(dir $(realpath $(lastword $(MAKEFILE_LIST))))
+BDJSDK_HOME  ?= $(MAKEFILE_DIR)/../../
+BDSIGNER     := $(BDJSDK_HOME)/host/bin/bdsigner
+MAKEFS       := $(BDJSDK_HOME)/host/bin/makefs
+JAVA8_HOME    ?= $(BDJSDK_HOME)/host/jdk8
+JAVAC        := $(JAVA8_HOME)/bin/javac
+JAR          := $(JAVA8_HOME)/bin/jar
+
+export JAVA8_HOME
+
+
+#
+# Compilation artifacts
+#
+CLASSPATH     := $(BDJSDK_HOME)/target/lib/enhanced-stubs.zip
+SOURCES       := $(wildcard src/org/homebrew/*.java)
+JFLAGS        := -Xlint:-options -source 1.3 -target 1.3
+
+
+#
+# Disc files
+#
+TMPL_DIRS  := $(shell find $(BDJSDK_HOME)/resources/AVCHD/ -type d)
+TMPL_FILES := $(shell find $(BDJSDK_HOME)/resources/AVCHD/ -type f)
+
+DISC_DIRS  := $(patsubst $(BDJSDK_HOME)/resources/AVCHD%,discdir%,$(TMPL_DIRS)) \
+              discdir/BDMV/JAR
+DISC_FILES := $(patsubst $(BDJSDK_HOME)/resources/AVCHD%,discdir%,$(TMPL_FILES)) \
+              discdir/BDMV/JAR/00000.jar
+
+
+all: $(DISC_LABEL).iso
+
+
+discdir:
+	mkdir -p $(DISC_DIRS)
+
+
+discdir/BDMV/JAR/00000.jar: discdir $(SOURCES)
+	$(JAVAC) $(JFLAGS) -cp $(CLASSPATH) $(SOURCES)
+	$(JAR) cf $@ -C src/ .
+	$(BDSIGNER) -keystore $(BDJSDK_HOME)/resources/sig.ks $@
+
+
+discdir/%: discdir
+	cp $(BDJSDK_HOME)/resources/AVCHD/$* $@
+
+
+$(DISC_LABEL).iso: $(DISC_FILES)
+	$(MAKEFS) -m 16m -t udf -o T=bdre,v=2.50,L=$(DISC_LABEL) $@ discdir
+
+
+clean:
+	rm -rf META-INF $(DISC_LABEL).iso discdir src/org/homebrew/*.class
+
+
+test: $(DISC_LABEL).iso
+	vlc $<

vendor/bdj-sdk/samples/helloworld/src/org/homebrew/LoggingUI.java

@@ -0,0 +1,82 @@
+package org.homebrew;
+
+import java.awt.Color;
+import java.awt.Container;
+import java.awt.Font;
+import java.awt.Graphics;
+import java.io.StringWriter;
+import java.io.PrintWriter;
+import java.util.ArrayList;
+
+public class LoggingUI extends Container {
+    private final Font font = new Font(null, Font.PLAIN, 14);
+    private final Color fontColor = new Color(240, 240, 240);
+    private final Color bgColor = new Color(5, 5, 5);
+    private final ArrayList rows = new ArrayList();
+    private static LoggingUI instance = null;
+
+    private LoggingUI() {
+    }
+
+    public static LoggingUI getInstance() {
+	if(instance == null) {
+	    instance = new LoggingUI();
+	}
+
+	return instance;
+    }
+
+    public void paint(Graphics g) {
+	g.setFont(font);
+	g.setColor(bgColor);
+	g.fillRect(20, 20, getWidth() - 40, getHeight() - 40);
+	g.setColor(fontColor);
+
+	for(int i=0; i<rows.size(); i++) {
+	    String row = (String)rows.get(i);
+	    int len = g.getFontMetrics().stringWidth(row);
+	    g.drawString(row, 30, 40 + (i*15));
+	}
+    }
+
+    public void log(String msg) {
+	rows.add(msg);
+	if(rows.size() > 45) {
+	    rows.remove(0);
+	}
+	repaint();
+    }
+
+    public void log(Throwable t) {
+	StringWriter sw = new StringWriter();
+	PrintWriter pw = new PrintWriter(sw);
+	StringBuffer sb = new StringBuffer();
+
+	t.printStackTrace(pw);
+	String st = sw.toString();
+
+	for(int i=0; i<st.length(); i++) {
+	    char ch = st.charAt(i);
+
+	    switch(ch) {
+	    case '\t':
+		sb.append("    ");
+		break;
+
+	    case '\n':
+		log(sb.toString());
+		sb = new StringBuffer();
+		break;
+
+	    default:
+		sb.append(ch);
+		break;
+	    }
+	}
+
+	if(sb.length() > 0) {
+	    log(sb.toString());
+	}
+    }
+}
+

vendor/bdj-sdk/samples/helloworld/src/org/homebrew/MyXlet.java

@@ -0,0 +1,46 @@
+package org.homebrew;
+
+import java.awt.BorderLayout;
+import javax.tv.xlet.Xlet;
+import javax.tv.xlet.XletContext;
+import org.havi.ui.HScene;
+import org.havi.ui.HSceneFactory;
+
+public class MyXlet extends Thread implements Xlet {
+    private HScene scene;
+    private LoggingUI logUI;
+    
+    public void initXlet(XletContext context) {
+	logUI = LoggingUI.getInstance();
+	logUI.setSize(1280, 720);
+	
+	scene = HSceneFactory.getInstance().getDefaultHScene();
+	scene.add(logUI, BorderLayout.CENTER);
+        scene.validate();
+	scene.repaint();
+    }
+    
+    public void startXlet() {
+	logUI.setVisible(true);
+        scene.setVisible(true);
+	start();
+    }
+    
+    public void pauseXlet() {
+	logUI.setVisible(false);
+    }
+    
+    public void destroyXlet(boolean unconditional) {
+	interrupt();
+	logUI.setVisible(false);
+	scene.remove(logUI);
+        scene = null;
+    }
+    
+    public void run() {
+	logUI.log("Hello, World!");
+    }
+}
+
+
+

vendor/bdj-sdk/samples/helloworld/src/org/homebrew/bluray.MyXlet.perm

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<n:permissionrequestfile xmlns:n="urn:BDA:bdmv;PRF" orgid="0x56789abc" appid="0x4000">
+    <file value="true"></file>
+    <applifecyclecontrol value="true"></applifecyclecontrol>
+    <servicesel value="true"></servicesel>
+    <userpreferences read="true" write="true"></userpreferences>
+    <bd-vfs value="true"></bd-vfs>
+    <network>
+	<host action="connect,resolve,listen">*</host>
+    </network>
+    <bd-bindingunitarea value="true" />
+</n:permissionrequestfile>