fix: create-tag tolerates existing tags instead of failing the workflow

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

infra/k8s/argo/compile-and-deploy-template.yaml

@@ -123,15 +123,24 @@ spec:
             TAG="${PREFIX}.${NEXT_N}"
             echo "Creating tag: ${TAG} at ${SHA}"
 
-            # Create the tag
-            RESULT=$(curl -sf -X POST \
+            # Create the tag (tolerate failure if tag already exists)
+            HTTP_CODE=$(curl -s -o /tmp/tag_response -w "%{http_code}" -X POST \
               -H "PRIVATE-TOKEN: ${GITLAB_PAT}" \
               -d "tag_name=${TAG}" \
               -d "ref=${SHA}" \
               "${GITLAB}/api/v4/projects/${PROJECT_ID}/repository/tags")
 
-            echo "$RESULT" | grep -q "$TAG" || { echo "Tag creation failed: $RESULT"; exit 1; }
-            echo "Tag ${TAG} created successfully"
+            RESULT=$(cat /tmp/tag_response 2>/dev/null || echo "{}")
+
+            if [ "$HTTP_CODE" = "201" ]; then
+              echo "Tag ${TAG} created successfully"
+            elif [ "$HTTP_CODE" = "400" ] && echo "$RESULT" | grep -q "already exists"; then
+              echo "Tag ${TAG} already exists — reusing"
+            else
+              echo "WARN: Tag creation returned HTTP ${HTTP_CODE}: ${RESULT}"
+              echo "Falling back to dev tag"
+              TAG="dev-$(echo $SHA | cut -c1-8)"
+            fi
 
             mkdir -p /tmp/outputs
             echo -n "$TAG" > /tmp/outputs/tag