feat: directory moves — mirrored batch relocation of every indexed file under a dir

- MovePlan gains moves[] (file move = 1 relocation), left_behind[] for
  unindexable files that deliberately stay, prune_dirs[] applied after the
  batch (remove_dir only succeeds when empty, leftovers keep their home)
- plan::dir: nesting/target-exists guards, merged per-file rewrites
- apply: atomic N-rename batch (per-file git mv), rollback restores every
  move, rewrite and created dir newest-first
- mv_reject accepts dirs; --json adds moved_files/would_move_files only for
  real dir moves (single-file contract byte-identical); summary shows
  (N files) and left-behind count
- engine rollback/prune tests moved to tests/apply.rs (public API; a
  mid-batch failure cannot be forced through the CLI), java-rule e2e split
  into its own binary to keep every file under the 250-line budget

docs/EXAMPLES.md

@@ -5,8 +5,8 @@ consuming `--json`. All outputs below are captured from the real binary.
 
 Flags (see `jmove --help`): `mv <source> <target> [--dry-run] [--json]
 [--no-git]`, `check [--json]`, and the global `--root <DIR>` /
-`--source-root <DIR>` (index one subtree only — the monorepo disambiguator
-for duplicate Java packages). `.gitignore`d files are never indexed. Inside a git repo, `mv` of a tracked file uses `git mv` (the
+`--source-root <DIR>` (monorepo subtree filter). `<source>` may also be a
+directory (mirrored batch move, emptied dirs pruned). Inside a git repo, `mv` of a tracked file uses `git mv` (the
 rename is staged); `--no-git` forces a plain filesystem rename.
 Exit codes: `0` ok · `1` operation error · `2` `check` found broken imports.