wwstage ran no operand-kind check on binary/unary operators: str+str
compiled to integer ADD on the 24B header (silent garbage). Gate each
operator class on the operand kind, mirroring cstage check.c:1186-1238
wording; the pre-existing ptr-arith arm aligns to intkindast so
ptr+untyped_int keeps compiling (byte-id-neutral, the over-reject the
self-compile gate caught). New intkindast/numkindast/boolkindast
predicates.
Hojun-Cho
353b50489f