Add stable/2026.1 jobs

The branch was created a while ago but hasn't been tested. Make sure
that the current tempest plugin is compatible with the branch.

Change-Id: I6ab71d4b1b17cd5fc22b9446b58dfee1a1bfec79
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

.zuul.d/jobs_2026_1.yaml

@@ -0,0 +1,23 @@
+---
+- job:
+    name: magnum-tempest-plugin-tests-api-2026-1
+    parent: magnum-tempest-plugin-tests-api-base
+    nodeset: openstack-single-node-noble
+    override-checkout: stable/2026.1
+    vars:
+      devstack_localrc:
+        MAGNUM_GUEST_IMAGE_URL: https://builds.coreos.fedoraproject.org/prod/streams/stable/builds/38.20230806.3.0/x86_64/fedora-coreos-38.20230806.3.0-openstack.x86_64.qcow2.xz
+      devstack_local_conf:
+        test-config:
+          $TEMPEST_CONFIG:
+            magnum:
+              image_id: fedora-coreos-38.20230806.3.0-openstack.x86_64
+
+- project-template:
+    name: magnum-tempest-plugin-jobs-2026-1
+    check:
+      jobs:
+        - magnum-tempest-plugin-tests-api-2026-1
+    gate:
+      jobs:
+        - magnum-tempest-plugin-tests-api-2026-1

.zuul.d/project.yaml

@@ -5,6 +5,7 @@
       - check-requirements
       - magnum-capi-helm-tests-cluster-v1_34
       - magnum-tempest-plugin-jobs-master
+      - magnum-tempest-plugin-jobs-2026-1
       - magnum-tempest-plugin-jobs-2025-2
       - magnum-tempest-plugin-jobs-2025-1
       - tempest-plugin-jobs