Add an NRW Abitur version of the library - #36

Courses in North Rhine-Westphalia use the classes of the Zentralabitur (List, Queue, Stack, Graph, …). They sit in the default package of the student's project, which a library can't reference by name. So find, getAll and getTouchingSprites could only return java.util.List, and this didn't compile:

List<Gegner> gegner = find(Gegner.class);
// error: incompatible types: java.util.List<Gegner> cannot be converted to List<Gegner>

What changes

There's now a second JAR. A course picks one by picking the JAR:

The rest of the API is the same in both, and the normal JAR's API doesn't change.

How it works

• Both versions in one source file: Java can't overload on return type, so Stage.java and Sprite.java hold both versions of each of the three methods. The NRW one sits in // nrw: comments between // nrw-standard-begin / // nrw-standard-end markers.
• Building the NRW JAR: src/tools/java/variants/NrwVariant.java copies the sources and swaps the two versions. The new nrw Maven profile compiles that copy instead of src/main/java, so mvn clean package -Pall,nrw produces scratch-<version>-nrw-all.jar and -nrw-sources.jar. That build skips tests, examples and the reference docs, which are written for java.util.List.
• At runtime: internal/NrwList looks up the class called List through the student's class loader. It creates one, fills it with append, and returns it as whatever type the student wrote on the left.
• The Abiturklassen aren't bundled. The official files carry no licence. A bundled List would also clash with the copy teachers already put in the project, since a class in the project takes priority over an import. The student's own copy is always the one used.

Other changes

• Release: release.yml builds the NRW JARs and attaches them to the GitHub release. Maven Central still gets only the normal version.

• Docs: a new Abiturklassen NRW page covers:

  • which JAR to use;
  • project setup, including where to get the Abiturklassen;
  • examples for all three methods, plus a Queue example;
  • how it works;
  • common errors.

  It's linked from Setup and Download.

• Build: pom.xml gets the nrw profile, and the shaded JAR's classifier is now configurable so the two fat JARs get different names.

• CLAUDE.md: documents the new build command.

• Changeset: minor.

Testing

• mvn test: 184 tests pass. 2 are skipped because they need Java 25; they're unrelated to this change.
• New NrwListTest covers the runtime lookup, including a missing List and a List without append.
• New NrwVariantTest checks the rewrite. It also builds the NRW sources and compiles a student program against them, so a change that breaks the NRW version fails the normal test run.
• Ran by hand under Xvfb with the unchanged official Abiturklassen and the NRW fat JAR:
  • find, getAll and getTouchingSprites returned the official List with the right sprites.
  • Queue, Stack and Graph work alongside the library with every extension package imported, with no name clashes.
• Against the normal JAR, the same project fails only on those three lines, as expected.
• Every code example on the new docs page compiles against the JAR it's written for.

Not tested: the release workflow change, which first runs on the next release, and running inside BlueJ itself.

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https://claude.ai/code/session_01KLR5H7eqDSncYYkosKf8r5