A successful PR merge was still leaving gx branch finish with a non-zero exit when the trailing remote branch delete raced with an already-removed ref. The cleanup step now treats that specific already-gone state as success while keeping other remote delete failures strict, and the finish suite now covers the race explicitly.

Constraint: branch-finish cleanup must stay strict for real remote delete failures while tolerating post-merge ref races
Rejected: ignore all remote delete failures with || true | would hide real cleanup regressions after merge
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: treat only the already-gone remote ref case as idempotent success; keep other push-delete errors fatal
Tested: bash -n scripts/agent-branch-finish.sh templates/scripts/agent-branch-finish.sh; node --test test/finish.test.js
Not-tested: full live branch finish against GitHub before this commit