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

03-behavioral/chain-of-responsibility/Level3Support.java

@@ -0,0 +1,15 @@
+package chain;
+
+/** Handles HIGH priority tickets — senior engineers */
+public class Level3Support extends SupportHandler {
+
+    @Override
+    protected boolean canHandle(SupportTicket ticket) {
+        return ticket.getPriority() == SupportTicket.Priority.HIGH;
+    }
+
+    @Override
+    protected void handle(SupportTicket ticket) {
+        System.out.println("  [Level-3] Engineering deep-dive completed: " + ticket);
+    }
+}