Reject helpers checked only rc!=0, so a SEGFAULT (exit 139, or the
driver's "w6c failed" exit 1) counted as a clean reject -- a wwstage
crash could pass vacuously (it did, latently, on bodied bare-... pre
#11). Every reject row now captures stderr and requires the actual
diagnostic substring (rc!=0 AND strstr) across all 16 reject tests; a
crash emits no diagnostic, so it now fails. This is the
differential-reject backstop (#15): both stages must cleanly reject
with the expected message.
Two genuine cstage/wwstage diagnostic-body divergences are documented
inline via per-stage substrings, not papered over (845 tuple parse,
catA_f2 tuple arity); catalogued in #21.
wwstage's tuple-parse loop checked the RPAREN-break at the top, so
`(a,)` parsed as a 1-element N_TUPLE and reached cgen — a silent
wrong-accept. A trailing comma is legal only after >=2 elements.
Align the loop order to cstage cmd/wcc/parse.c:552-558 (parse each
element before the RPAREN-break); `(a,)` now errors at the next
parseexpr, `(a, b)` / `(a, b,)` are unchanged. cstage already
rejected; this brings wwstage's w6c_ww parser into agreement.
Regen w6c/wwdump combined.ww (parser embeds in both). Valid-program
codegen unchanged → cs==ww byte-id gate stays green.
