Three more wwstage cgen sites still used unrounded structnaturalsize where
cstage rounds via lu->size — pre-existing gate-blind cs!=ww latents the #169b
reviewer surfaced: cgenstmt N_LET struct-IDENT memcpy (let p2: T = p1; twin
cgen.c:7869), cgenexpr N_ASSIGN N_IDENT-lhs register RECV (s = mk(); twin
cgen.c:4700-4737), and cgenutil's nested struct N_CALL recv inside
cgstructlitfill (twin cgen.c:2121).
Converge all three onto structabisize, completing the same-class closure
started by #169 and continued by #169b. Also corrected the inline comment at
cgenutil.ww:3273-3286 that wrongly claimed fl->type->size was natural
(check.c:760 sets ABI). sretretsize at cgenutil.ww:1301 is gate-equivalent
natural and is left alone.
Probe 698 +3 rows (one per converged site) with cs==ww .s byte-cmp and a
pre-fix-rebuild discriminator. 990-997 byte-id hold.