Twin of #134 (N_INDEX arm): the wwstage signedness classifier did not
consult the checker-stamped type_ for an N_CALL result, so an
unsigned-returning call got signed IDIVQ/SARQ instead of DIVQ/SHRQ.
cstage was already correct (reads the stamped operand type; check.c:1433),
so this is a wwstage-only arm — symmetric outcome both stages.
Gate-blind (the bootstrap lacks the shape) — covered by table-driven
runtime probe 906, which also asserts w6c==w6c_ww .s byte-identity.
Hojun-Cho
393ac1a882