Dropping the length check left nothing checking the reply against the
request at all: AcknowledgeResult::validate_against existed with no
caller, so a worker could acknowledge ids this session never asked
about. That is the other half of the rule the README states. A short
list is the worker reporting what it released and is accepted; an id
from outside the request is the worker reporting about someone else's
cache and is refused, named, before any mutation.
The bootstrap-path regression is now covered too. The earlier test calls
acknowledge_replies directly, which guards the check where it lives but
not where it lived, so a length check put back into acknowledge_lifecycle
left it green. The duplicate_lifecycle_acknowledge injection releases the
ids first, out of sight, so the call that method makes and checks is
already the second one -- the shape the section 6 resolution produces.
Verified by putting the old check back: three tests fail with it, none
without.
Also: last_resolution_attempts is cleared with last_resolution, so a
resolution ending before its first attempt no longer reports the
previous count; the guard half of the bound test asserts the fence like
the budget half; the attempts assertion checks a real bound rather than
u32::MAX; and two dead Instant bindings are gone.