test: PoC publish via artifact-gateway with dd-pkg image

Replace publish_public_main trigger block with dd-pkg publish-image.
Uses staging gateway, test destination (agent-dev:gateway-operator-poc-test),
registry.datad0g.com only. Manual trigger for safety.

BARX-1709

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: AliDatadog

.gitlab-ci.yml

@@ -478,6 +478,24 @@ publish_public_main:
     IMG_SIGNING: "false"
     IMG_MERGE_STRATEGY: "index_oci"
 
+# PoC: publish via artifact-gateway instead of direct public-images trigger.
+publish_via_gateway_poc:
+  stage: release
+  image: registry.ddbuild.io/agent-delivery/dd-pkg:v106852116-3c888529
+  tags: ["arch:amd64"]
+  rules:
+    - when: manual
+      allow_failure: true
+  before_script: []
+  variables:
+    IMG_SOURCES: $BUILD_DOCKER_REGISTRY/$PROJECTNAME:v${CI_PIPELINE_ID}-${CI_COMMIT_SHORT_SHA}-amd64
+    IMG_DESTINATIONS: operator-dev:gateway-poc-${CI_PIPELINE_ID}
+    IMG_REGISTRIES: "registry.datad0g.com"
+    IMG_SIGNING: "false"
+    ARTIFACT_GATEWAY_URL: "https://artifact-gateway.us1.ddbuild.staging.dog/internal/artifact-gateway"
+  script:
+    - dd-pkg publish-image --gateway-url "${ARTIFACT_GATEWAY_URL}" --timeout 1800
+
 publish_public_main_fips:
   extends: publish_public_main
   variables: