Port ref/hare/strconv/stou.ha:8-65 (rune_to_integer + parseint) and the
stoi64/stou64 fidelity rewrite (stoi.ha:9-17, stou.ha:70-76) over the old
digval loop. parseint is the shared sign + per-digit + multiply-overflow
core returning ((bool, u64) | invalid | overflow); stoi64/stou64 destructure
its `(sign, u)` tuple-in-union result — the shape unblocked by #242/#241.
Wins over the prior ad-hoc parse: leading '+' accepted, '-' on stou64 is
overflow (not silently dropped), wraparound overflow detection (n < old),
and the invalid payload carries the offending byte index per Hare.
Tests: lib/strconv/test/inttest.ww (run via test/wcc/922_strconv_int_run.c),
inline per-case checks mirroring Hare's assert sequences stoi.ha:56-86 /
stou.ha:116-138 (Hare's strconv int tests are flat sequences, not row
tables; feedback_test_match_hare_source). Covers valid dec/hex/oct/bin,
+/- sign, invalid+index, overflow, and U64_MAX / I64_MAX / I64_MIN
boundaries. The I64_MIN expectation is spelled -I64_MAX-1 (Hare's own
two's-complement identity) to isolate the test from #245 (wwstage mis-lexes
the literal 9223372036854775808 -> 0); the parse INPUT is unaffected and
yields the correct value on both stages.
combined.ww regen: strconv is compiler-imported (via fmt), so w6c +
wwdump main.combined.ww are regenerated.
Hojun-Cho
6a5cdbd779