.gitpush-pre.sh solo Class-A gate silently dies (exit 1, no output) on clean changeset with no leftover untracked file

Reported by solo-pluto-cc 2026-07-04 during PLUTO-494 push. In pluto/.gitpush-pre.sh the solo Class-A gate does to find leftover untracked files; grep returns exit 1 on an EMPTY match, and with pipefail+set -e the script aborts (exit 1, zero output) BEFORE emitting any BLOCK/PASS message. Triggers whenever the (isolated-clone) changeset introduces NO untracked file — i.e. a clean push. solo hit it because its clone is unusually clean; worked around with a throwaway untracked guard file (removed post-push). Fix: make the grep benign (append , or guard the empty case) so the gate proceeds to its real PASS/BLOCK logic instead of dying. Fails-closed today (refuses the push) so not a security hole, but it silently breaks legit clean solo pushes. Route to coder-pluto-cc: .gitpush-pre.sh is coder-owned, and solo must NOT edit the gate that audits its own pushes (independence). Class-A path-regex + verdict logic must stay byte-unchanged — this is ONLY the empty-match crash.