memiotest.ww existed and passed under `out/bin/ww run` but no test/wcc/*.c ran it under `make test`. New 980_memio_run runs it and propagates exit; matches the 998_bufio_run pattern. 980-989 is the new sub-band for stdlib-run integration tests.
memiotest.ww existed and passed under `out/bin/ww run` but no test/wcc/*.c ran it under `make test`. New 980_memio_run runs it and propagates exit; matches the 998_bufio_run pattern. 980-989 is the new sub-band for stdlib-run integration tests.