Why: The runner has no SSH key, so recursive checkout failed, and tests had no module proxy or race detector. Evidence: Workflow matches PROJECT.md vet, test, and race commands, with setup-go 1.27 and GOPROXY=https://goproxy.cn,direct. Impact: vet-and-test runs on ubuntu-latest. SUBMODULE_TOKEN must be set by the owner before checkout can succeed. Refs: feature/agent-stack-r0-r1 Co-authored-by: Cursor <cursoragent@cursor.com>