Add jep512 module: compact source files and instance main methods on JDK 25 and 27

Runnable sources, broken examples and captured transcripts for the ankurm.com JEP 512 article,
including the measured launch order and a private-constructor difference between 25 and 27.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01TF9JWFvJSNm6HVzswzZU5a

jep512/output/01-source-launcher.txt

@@ -0,0 +1,22 @@
+$ cat src/Hello.java
+// The smallest complete Java 25 program. No class, no public, no static, no String[] args.
+void main() {
+    IO.println("Hello, world");
+}
+
+$ java src/Hello.java        (JDK 25: OpenJDK Runtime Environment Temurin-25.0.4.1+1 (build 25.0.4.1+1-LTS))
+Hello, world
+
+$ java src/Hello.java        (JDK 27: OpenJDK Runtime Environment Temurin-27+35 (build 27+35))
+Hello, world
+
+$ ls src/*.class
+  ls: cannot access 'src/*.class': No such file or directory
+
+$ java src/Hello.java        (JDK 21: OpenJDK Runtime Environment (build 21.0.10+7-Ubuntu-124.04))
+src/Hello.java:2: error: unnamed classes are a preview feature and are disabled by default.
+void main() {
+^
+  (use --enable-preview to enable unnamed classes)
+1 error
+error: compilation failed