test(raft-apply-decoupling): idempotent and ordered re-application of apply seam (task 2.4)

Add test_apply_reapply_idempotency.c (3 tests, no production changes):
triple-reapplication of an identical job submit with hook-count and
pointer-identity assertions across every call, the NOOP_DUPLICATE
guard branch (untested by task 2.2), and the task's named scenario --
real SUBMIT then real FINISH then a stale out-of-order START, all
through the real apply_committed_entry() dispatch -- confirming the
job stays terminal with no spurious notification.

Closes out task-group 2 (shared apply seam for committed entries).

src/controller/meson.build

@@ -160,6 +160,7 @@ controller_unit_test_src = [
   'testsuite/test_apply_seam.c',
   'testsuite/test_apply_committed_entry.c',
   'testsuite/test_replay_apply_seam.c',
+  'testsuite/test_apply_reapply_idempotency.c',
   'ctrlstatus.c',
   'commit.c',
   'job.c',