argus, reviewing, ran the guard against a source path that does not
exist rather than one that is empty. grep writes nothing to stdout in
that case, so `|| true` left the count variable empty and the -eq test
died with "integer expected" instead of reporting.
The unit still failed — cat hits the same missing file and set -e stops
it — but with a generic "no such file" rather than the message naming
which half is absent, which is the only thing this guard is for.
`|| echo 0` on all three counts. The gate gained the arm that was
missing: an absent source, asserted to fail THROUGH the guard rather
than merely to fail.
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