Add all 23 GoF design pattern implementations (2026-06-13)

02-structural/decorator/PlainTextProcessor.java

@@ -0,0 +1,14 @@
+package decorator;
+
+/**
+ * Concrete Component — the base object being decorated.
+ * Does nothing special: just returns the text as-is.
+ * All decorators wrap this (or other decorators on top of it).
+ */
+public class PlainTextProcessor implements TextProcessor {
+
+    @Override
+    public String process(String text) {
+        return text;  // base: no transformation
+    }
+}