Hojun-Cho
6a5cdbd779
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.