Fix playListNumber to stream-name mapping; add JavaFX ui module

- Playlist.streamForPlayListNumber maps the 1-based playListNumber to the
  actual stream entry; stream names are not sequential across discs
  (The Dark Knight: 00001/00003/00004; The Day After Tomorrow has
  duplicate 00002 names).
- CLI menu playback now resolves the correct .MPS file for every region.
- ui module: JavaFX via org.openjfx.javafxplugin + PlayerApp smoke test
  (window verified on this display).
- Validated menus + playback on 4 discs: Batman Begins (USA), Jackass
  (Australia), The Dark Knight (Europe), The Day After Tomorrow (Japan).

ui/build.gradle.kts

@@ -1,5 +1,6 @@
 plugins {
-    `java-library`
+    application
+    id("org.openjfx.javafxplugin") version "0.1.0"
 }
 
 java {
@@ -7,3 +8,16 @@ java {
         languageVersion = JavaLanguageVersion.of(21)
     }
 }
+
+javafx {
+    version = "21.0.5"
+    modules("javafx.controls")
+}
+
+application {
+    mainClass = "dev.quoije.umd.ui.PlayerApp"
+}
+
+dependencies {
+    implementation(project(":core"))
+}

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

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+package dev.quoije.umd.ui;
+
+import javafx.application.Application;
+import javafx.application.Platform;
+import javafx.scene.Scene;
+import javafx.scene.control.Label;
+import javafx.scene.layout.StackPane;
+import javafx.stage.Stage;
+
+import java.util.List;
+
+/** JavaFX application entry point for the UMD player. */
+public final class PlayerApp extends Application {
+
+    @Override
+    public void start(Stage stage) {
+        List<String> params = getParameters().getRaw();
+        String imagePath = params.isEmpty() ? null : params.get(0);
+
+        StackPane root = new StackPane(new Label("useless-umd-player\n" + (imagePath == null ? "(no iso)" : imagePath)));
+        stage.setTitle("useless-umd-player");
+        stage.setScene(new Scene(root, 854, 480));
+        stage.show();
+
+        // Temporary smoke test: auto-close after 2 seconds.
+        new Thread(() -> {
+            try {
+                Thread.sleep(2000);
+            } catch (InterruptedException ignored) {
+            }
+            Platform.exit();
+        }, "smoke-close").start();
+    }
+
+    public static void main(String[] args) {
+        launch(args);
+    }
+}