cstage zeroed the return scratch; mirror the landed wwstage emission
(copy from the g(SB) base). Flips the F8-era residual row to
cs==ww==correct. Task #42.
Returning a global struct by name emitted nothing into the return
scratch (ww) — copy from the g(SB) base. Both-wrong pair: cstage
zeroes the retscr instead (filed task #42); rows pin ww-runtime-correct
with the documented cstage residual. Review item #41.
