boundedIntegerLoopFacts only accepted constant positive steps, so the
sieve's inner loop `for (let j = i * 2; j <= LIMIT; j += i)` kept j a
double: addsd, a floating bound compare, and an fptosi/sitofp exactness
check on every typed-array index.
A step may now be a binding the loop never writes (stable: not boxed,
TDZ or captured) whose entry fact is a positive integer range up to
2^31 - 1, added (or a negative range subtracted). Each update then adds
an exact integer in that range, so the counter climbs from its start to
at most the limit plus the largest step; the iteration budget for
secondary cursors uses the smallest step. j becomes an i32 slot updated
with add nsw i32.
Corpus 5322 pins zero, -0, negative, fractional, NaN and infinite steps,
steps written by the body, early exits, and counters crossing 2^31, 2^32
and 2^53 against Node.
