Iterator: sync post code blocks to repo exactly, Java 25, add H6 file labels and README mapping, fix stale console output

README.md

@@ -338,6 +338,23 @@ javac 03-behavioral/command/*.java -d out/command
 java -cp out/command command.Main
 ```
 
+### Iterator (`03-behavioral/iterator/`)
+
+| Post Section | File(s) |
+|---|---|
+| Custom Iterator Implementation — the Iterator interface | `BookIterator.java` |
+| Custom Iterator Implementation — the element type | `Book.java` |
+| Custom Iterator Implementation — the Aggregate (BookShelf, ForwardIterator, DecadeIterator) | `BookShelf.java` |
+| Custom Iterator Implementation — wiring it together | `Main.java` |
+
+Note: the "How Java's For-Each Loop Uses Iterator" snippet (`Iterable<Book>` example) is illustrative only — it is not part of this repository's runnable example.
+
+Run it:
+```bash
+javac 03-behavioral/iterator/*.java -d out/iterator
+java -cp out/iterator iterator.Main
+```
+
 ## Reference
 
 - *Design Patterns: Elements of Reusable Object-Oriented Software* — Gamma, Helm, Johnson, Vlissides