Continue fold-2: migrate the #73 whole-struct field-copy ragged-tail test from a
bespoke build+run C twin to test/lang @test, retiring the twin in the same
commit. Runtime coverage MOVES from $(TESTS) to test-lang (T1 runs+asserts via
`ww test`) + test-lang-byteid (T2 keeps cs==ww .s byte-id); coverage is
preserved, the $(TESTS) headline drops 1 (422->421). All four rows are pure
value-rows (no reject rows): each poisons `mark` at the inner struct's natural
offset, copies, then asserts every field back with primitive int comparisons, so
an 8-byte MOVQ that over-writes the ragged-tail successor FAILS.
989_structcopytail_run.c -> structcopytail_test.ww (tail2/tail6/tail7 ragged-tail copy preserves mark; ctl8 8-aligned control)
This is the only Family-3 file with no build-must-fail rows; the three
compound-OP= twins (948_idx_compound, 949_dotfield_compound, 949_idxfield_compound)
carry loud //ww:error reject rows a runtime @test cannot replicate and are
DEFERRED to a fold-3 value-split + reject-carrier pass (they stay fully in
$(TESTS), no coverage lost).
Bump LANGBYTEID_EXPECTED_MIN 34->35 to ratchet the new corpus floor.
Hojun-Cho
b879d38b0f