Hojun-Cho
e9bd06a193
The port shipped sum() single-shot — mutating the live hash state —
because Hare's state snapshot `let copy = *h; let h = ©` (a
deref-rhs aggregate let-init of an array-containing struct) miscompiled
in cgen. #265 fold-1 (master 4d3f846) landed the full-size aggregate
copy for that axis, so restore the faithful form: pad+finalize the
snapshot, leave the live state untouched, close() the copy.
sum() is now non-destructive — summing twice yields the same digest and
writing after a sum() continues the stream. Pinned by a new reentrant()
@test (sum-twice identical + write-after-sum continuity). NIST vectors
unchanged.