Base: BD-J Adjustments Blu-ray scaffold

Vendored BD-J SDK, tsMuxeR + local VLC plugins, ffmpeg asset generation,
and a signed BD-J Xlet menu (org.homebrew.MyXlet) authored into a UDF 2.50 ISO.

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

vendor/bdj-sdk/host/bin/bdsigner

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+SCRIPTDIR="${BASH_SOURCE[0]}"
+SCRIPTDIR="$(dirname "${SCRIPTDIR}")"
+LIBDIR=${SCRIPTDIR}/../lib
+
+if [ "${JAVA8_HOME}" != "" ]; then
+    JAVA=${JAVA8_HOME}/bin/java
+else
+    JAVA=java
+fi
+
+$JAVA -cp ${LIBDIR}/'*' net.java.bd.tools.security.BDSigner $*
+