fix(builder): use a local node-agent image when it can't be pulled

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/agentboot.go

@@ -21,6 +21,20 @@ func agentImageFromEnv() string {
 	return defaultAgentImage
 }
 
+// pullAgentImage fetches the latest node-agent image. A copy that is only local (a test build) is used as
+// it is.
+func pullAgentImage(img string) error {
+	out, err := runCmd("docker", "pull", "-q", img)
+	if err == nil {
+		return nil
+	}
+	if _, inspectErr := runCmd("docker", "image", "inspect", img); inspectErr == nil {
+		fmt.Printf("[agent] could not pull %s (%s); using the local copy\n", img, firstLine(out))
+		return nil
+	}
+	return fmt.Errorf("docker pull %s: %v: %s", img, err, out)
+}
+
 // runAgentBootTest deploys a payload with BootTest and returns its output; passed is its verdict.
 func runAgentBootTest(payload map[string]any, agentImage string) (output string, passed bool, err error) {
 	container := fmt.Sprint(payload["containerName"])