wcc: drop @test fns from non-T builds, both stages (harec check.c:3941)

Splice @test N_FNDECLs out of the unit after the body-check passes,
mirroring harec's checked-but-not-emitted: a broken @test body still
errors loudly in non-T; @test-free units are emission-unchanged.
910/997 table rows pin keep/test x non-T/-T, head+consecutive unlink,
undef-body reject, and plain-calls-dropped loud link-fail. w6c+wwdump
combined.ww regen. (#6-team)

test/wcc/data/attest_undefbody.ww

@@ -0,0 +1,17 @@
+// #6 fixture: a @test body is type-checked in a non-test build even
+// though the fn is then spliced out. harec checks the body
+// (ref/harec/src/check.c:3913) BEFORE the append_decl skip (:3941), so
+// the splice is check-THEN-drop, never drop-then-skip-check. Pins that
+// placement decision: an undefined symbol in the @test body must be
+// caught LOUDLY in non-T (a pre-pass splice would silence it). Compiled
+// WITHOUT -T (910/997 plain-reject row).
+
+package data;
+
+fn keep() i32 = {
+	return 1;
+};
+
+@test fn undefbody_test() void = {
+	undefined_symbol_xyz();
+};