补充部署合同失败恢复说明（08-02-deployment-preflight-backup-contract-refresh）

scripts/refresh-deployment-contract.sh

@@ -30,6 +30,9 @@ fail() {
   exit "$code"
 }
 
+# Exit 255 is reserved for the SSH client transport layer. Do not use it for
+# helper failures, because callers classify 255 as root_identity_unavailable.
+
 if [[ "$(id -u)" != "0" ]]; then
   test_root="${HYB_CONTRACT_REFRESH_TEST_ROOT:-}"
   if [[ "$test_root" =~ ^/tmp/[A-Za-z0-9._/-]+$ && "$test_root" != */ \