feat(check): java public-class ⇄ file-name mismatch — layout finding with a ready jmove mv repair

- parser::java::class_name: exactly-one-public-top-level-type rule
  (package-info/module-info and 0-or-2-public files skipped)
- check gains name_mismatches[] (JSON, omitted when clean) + human lines;
  exit 2 covers both kinds; fix engine untouched by design — a file rename
  is not a byte edit, and mv keeps the FQN so no imports change
- output split into output/{mod,check} to stay under the 250-line rule
- e2e: reports Bad.java, stays quiet on Good.java, suggested rename makes
  check pass and preserves the file bytes

tests/java/mismatch/src/main/java/com/example/Bad.java

@@ -0,0 +1,3 @@
+package com.example;
+
+public class Wrong {}

tests/java/mismatch/src/main/java/com/example/Good.java

@@ -0,0 +1,3 @@
+package com.example;
+
+public class Good {}