Facade: split subsystem into one class per file, sync post code blocks to Java 25, add README mapping

02-structural/facade/MPEG4CompressionCodec.java

@@ -0,0 +1,6 @@
+package facade;
+
+/** Concrete Codec: MPEG-4 compression. */
+class MPEG4CompressionCodec implements Codec {
+    @Override public String getName() { return "mpeg4"; }
+}