48b48a8481
`ls -1dt run-*` returns both the per-run directories AND the
`.stdout.log` files run-matrix.sh tees alongside them, interleaved by
mtime. `head -n 1` could land on a `.stdout.log` regular file, after
which the rest of the script trying to walk subdirectories under it
silently produced empty output ("no <pair> dir under …"). Walk the
listing instead and pick the first entry that is actually a directory.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>