concat(a, b: str) -> concat(strs: str...) per ref/hare/strings/concat.ha:5.
Drop nomem return per project no-alloc-error idiom (os.alloc aborts).
Unblocked by #16 variadic-pack store fix (3bd9b1d).
concat_cases rewritten to table-driven: flat pool + argo/argn parallel
arrays + slice-spread call. 9 rows cover Hare concat.ha:18 vectors
(0/1/2/3-arg, multibyte) plus empty-mid/first/last/2-empty edges.
Bisect via signalled = 200 + i.
trim/contains variadic held on task #36 — surfaced by worker-variadic
pre-flight: iter + match prev composition in non-leaf callees still
hits scanlocals offset divergence. Resolves via #15 size-strategy.
make test 121/121; ww2==ww3==ww4 byte-id holds.
Hojun-Cho
5466ea048d