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).
