test: migrate Fam8 tuple value tests to @test + reject carriers (#5-C2)

fold-2 chunk C2 (drew's Fam8-13 plan): 14 tuple value-row C drivers migrate to
15 test/lang/*_test.ww @test row-tables (the +1 is 954_tuprecv, slimmed not
deleted -- its value rows split out while the asserttyped-stamp dimension stays
as a carrier-split C pin, mutation-proven non-vacuous). Reject rows move to 32
test/wcc/data/*/case.ww //ww:error carriers (runww asserts the substring in
BOTH stages). The test-lang byte-id (LANGBYTEID) gate gives cs==ww automatically
and is strictly more sensitive than re-running the wwstage leg; floor 59->74.
Tuple surfaced zero cs!=ww as the plan predicted -- no value-only carve. The 945
trio folds in here; 940_global_sret / 940_str_forrange / 926_tagscr untouched
(routed to drew per-file). Test count 402->388 = the 14 retired drivers.

test/wcc/data/tslot_t2_reject_nested_elem_arg/case.ww

@@ -0,0 +1,11 @@
+//ww:error "tuple element must be a scalar"
+package main;
+fn f(t: ((i64, i64), i64)) i64 = {
+	return t.1;
+};
+export fn main() i32 = {
+	let inner: (i64, i64) = (1, 2);
+	let t: ((i64, i64), i64) = (inner, 9);
+	if (f(t) != 9) { return 1; };
+	return 0;
+};