wwstage's checkretassign short-circuited on a value-less `return;`
("skip flagging for now"), so `fn f() i32 = { return; }` built and
RET'd a garbage register. Mirror cstage cmd/wcc/check.c:2428-2439:
the no-value return has type void, then run isassignable(c.fnret,
void) — void→void and void→(T|void) accept, void→i32 is a confident
reject. cstage already rejected; this aligns wwstage's w6c_ww UP.
Regen w6c/wwdump combined.ww (checker embeds in both). Valid-program
codegen unchanged → cs==ww byte-id gate stays green.
Hojun-Cho
d0adfe5aab