A bulk command with N denied items wrote N audit events into the bounded,
drop-on-full audit channel, so a low-privilege key could evict every other
pending audit record. Bulk filters now accumulate a ConstraintDenialSummary
(count, constraint names, <=20 sample targets) and write one aggregated
constraint-denied event per command.
The per-item constraint checks are synchronous, so IConstraintEnforcer's
Check* methods now return ValueTask instead of allocating a Task per item.
Joseph Doherty