Why: The runner cannot reach github.com, so cloning actions/checkout timed out before any test ran. Evidence: The Go 1.27.1 tarball is available from mirrors.aliyun.com. Checkout uses the job token and GITHUB_SHA. Impact: Submodule checkout still requires SUBMODULE_TOKEN. A missing secret fails the job with that message. Refs: feature/agent-stack-r0-r1 Co-authored-by: Cursor <cursoragent@cursor.com>