fix(test): build missing Docker images in Testbox

scripts/lib/docker-build.sh

@@ -6,6 +6,19 @@ if ! declare -F run_logged >/dev/null 2>&1; then
   source "$DOCKER_BUILD_LIB_DIR/docker-e2e-logs.sh"
 fi
 
+docker_build_on_missing_enabled() {
+  case "${OPENCLAW_DOCKER_BUILD_ON_MISSING:-}" in
+    1 | true | TRUE | yes | YES)
+      return 0
+      ;;
+    0 | false | FALSE | no | NO)
+      return 1
+      ;;
+  esac
+
+  [ "${OPENCLAW_TESTBOX:-0}" = "1" ]
+}
+
 docker_build_exec() {
   local build_cmd=(docker build)
   if [ "${OPENCLAW_DOCKER_BUILD_USE_BUILDX:-0}" = "1" ]; then