Add Fetch Disks button and Anleitung copy-protection viewer

- Cross-compile nibtools for Android NDK; download all 8 episode disks
  from the Internet Archive C64 Preservation Project as NBZ and convert
  to G64 via JNI (throwaway-pthread to contain nibconv's exit() calls)
- Bundle manual transcription as APK asset; 📖 button opens scrollable
  viewer with Seite→Absatz→Zeile→Wort lookup hierarchy documented

SchwertUndMagieOnPebbleCompanionApp/app/build.gradle.kts

@@ -122,11 +122,77 @@ tasks.register("buildVice") {
     }
 }
 
-// Run buildVice before any CMake configure or build step.
+// ---------------------------------------------------------------------------
+// nibtools cross-compilation task
+//
+// Builds nibconv (NIB/NBZ -> G64/D64 disk image conversion, used by the
+// "Download Disks" feature) the same way buildVice builds VICE above.
+// Skipped entirely if nibtools-libs/<abi>/libnibtools.a already exists.
+// The tarball at <project>/res/nibtools-91344e0ee3.tar.gz is unpacked by
+// build_nibtools.sh.
+// ---------------------------------------------------------------------------
+
+val nibtoolsLibArm  = layout.projectDirectory.file("src/main/jni/nibtools-libs/arm64-v8a/libnibtools.a")
+val nibtoolsLibX86  = layout.projectDirectory.file("src/main/jni/nibtools-libs/x86_64/libnibtools.a")
+val nibtoolsTarball = layout.projectDirectory.file("../res/nibtools-91344e0ee3.tar.gz")
+
+tasks.register("buildNibtools") {
+    group = "build"
+    description = "Cross-compile nibtools' nibconv for Android (ARM64 + x86_64)"
+
+    inputs.file(nibtoolsTarball)
+    outputs.file(nibtoolsLibArm)
+    outputs.file(nibtoolsLibX86)
+
+    doLast {
+        if (nibtoolsLibArm.asFile.exists() && nibtoolsLibX86.asFile.exists()) {
+            logger.lifecycle("nibtools already built — skipping")
+            return@doLast
+        }
+
+        val localProps = Properties().apply {
+            rootProject.file("local.properties").takeIf { it.exists() }
+                ?.reader()?.use { load(it) }
+        }
+        val sdkDir = localProps.getProperty("sdk.dir")
+            ?: System.getenv("ANDROID_HOME")
+            ?: ""
+        val ndkPath = localProps.getProperty("ndk.dir")
+            ?: System.getenv("ANDROID_NDK_HOME")
+            ?: System.getenv("ANDROID_NDK_ROOT")
+            ?: System.getenv("NDK")
+            ?: sdkDir.takeIf { it.isNotEmpty() }?.let { sdk ->
+                file("$sdk/ndk").takeIf { it.isDirectory }
+                    ?.listFiles()?.sorted()?.lastOrNull()?.absolutePath
+                    ?: "$sdk/ndk-bundle".takeIf { file("$sdk/ndk-bundle").isDirectory }
+            }
+            ?: throw GradleException(
+                "Android NDK not found.\n" +
+                "Install via: Android Studio → SDK Manager → SDK Tools → NDK (Side by side)"
+            )
+        logger.lifecycle("Building nibtools with NDK at $ndkPath …")
+
+        val proc = ProcessBuilder("bash", "build_nibtools.sh")
+            .directory(layout.projectDirectory.dir("src/main/jni").asFile)
+            .redirectErrorStream(true)
+            .also { it.environment()["NDK"] = ndkPath }
+            .start()
+        proc.inputStream.bufferedReader().forEachLine { logger.lifecycle(it) }
+        val exit = proc.waitFor()
+        if (exit != 0) throw GradleException("build_nibtools.sh failed (exit $exit)")
+
+        layout.projectDirectory.file("src/main/jni/CMakeLists.txt")
+            .asFile.setLastModified(System.currentTimeMillis())
+        logger.lifecycle("nibtools build complete — CMakeLists.txt touched for re-evaluation")
+    }
+}
+
+// Run buildVice and buildNibtools before any CMake configure or build step.
 tasks.whenTaskAdded {
     if (name.startsWith("configureCMake") || name.startsWith("buildCMake") ||
         name.startsWith("externalNativeBuild")) {
         dependsOn("buildVice")
+        dependsOn("buildNibtools")
     }
 }