Add patterns module: pattern matching from JDK 21 to 27

Type, record and primitive patterns, guards, sealed exhaustiveness, MatchException via separate compilation, and eight captured transcripts.

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

patterns/broken/Dominated.java

@@ -0,0 +1,10 @@
+public class Dominated {
+    static String f(Object o) {
+        return switch (o) {
+            case CharSequence cs -> "chars";
+            case String s -> "string";      // String is a CharSequence, so this can never be reached
+            default -> "other";
+        };
+    }
+    public static void main(String[] args) { System.out.println(f("x")); }
+}