Forward stub trace variables into the clean serve process

Why: env -i dropped SVC_STUB_*, so recovery tests saw an empty serve record even though the bound DSN was still passed.
Evidence: SELF python3 -m unittest tests.test_svc.SvcDbRecoveryTests tests.test_svc_lifecycle_isolation — 34 tests OK.
Impact: only SVC_STUB_* is added at launch; serve.env still omits them, and caller AGENT_SYSTEM_* stays out of the process.
Refs: #485
Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/svc.sh

@@ -1394,6 +1394,13 @@ svc_launch_serve() {
   if [ "${#guard_env[@]}" -gt 0 ]; then
     args+=("${guard_env[@]}")
   fi
+  # 桩只靠 SVC_STUB_* 找到记录目录。这些变量不写入 serve.env，避免 recover
+  # 把某次测试路径固化进实例；生产调用方没有它们。
+  local k
+  while IFS= read -r k; do
+    [ -n "$k" ] || continue
+    args+=("$k=${!k}")
+  done < <(compgen -e | grep -E '^SVC_STUB_' || true)
   # shellcheck disable=SC2086
   nohup "${args[@]}" "$ENV_BIN" serve $exec_args >> "$ENV_DIR/svc.log" 2>&1 9>&- &
 }