test: migrate 24 residual carriers into the fixture corpus

Audit-driven migrate-and-retire wave (one read-only auditor per
carrier batch, verdicts row-checked through the full corpus gate):
every retired carrier's assertions are now owned by declarative
fixtures or an existing owner. 238 new fixtures land (corpus 1,239 ->
1,477; cells 2,954), covering enum/str/slice/tagged array elements,
inferred-length arrays, global slice/str zero-init and literals,
global array/pointer field reads and stores, struct-literal slice
fields, struct returns, float arithmetic, size/int limits, sort and
log-vstream behavior, place-addressed stores, and append places.
Rejection rows STRENGTHEN the old nonzero-exit checks to required
diagnostic fragments; all byte-id claims fold into the blanket
test-data-byteid sweep (now 1,142 compared, 0 pinned-divergent).
Four carriers were fully redundant with existing fixtures/lang tests
(749, 722, 765, and 771's byteid rows) and retire without new rows.
Native carriers 171 -> 147 (residual 135 -> 111).

test/wcc/data/r805_arr_field_idx_store/case.ww

@@ -0,0 +1,13 @@
+//ww:run-exit 58
+package main;
+type t = struct { pc: size, matched: bool };
+type holder = struct { arr: [3]t, n: i64 };
+export fn main() i32 = {
+	let h: holder = holder { n = 0, ... };
+	h.arr[1].pc = 5;
+	h.arr[1].pc += 2;
+	if (h.arr[1].pc != 7) { return 1; };
+	if (h.arr[0].pc != 0) { return 2; };
+	if (h.arr[2].pc != 0) { return 3; };
+	return 58;
+};