AddJournal's Disposable.Create counted a refused dispose (from inside a journal
or another cache's hold) as done, leaving the journal registered forever. A
private registration now flips only after the removal succeeded. Held's catch
path dropped the hold's journal failures; it now throws an AggregateException
with the body's exception first. The store-composition contract states exactly
when the second getter read runs on a conditional commit. Adds the direct test
that a load is journaled.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>