Add skip level upgrade job

2026.1 is the release which supports SLURP from 2025.1 .

Change-Id: I322a9324a2181f511710bc028bf4f36d4252e4b7
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

.zuul.yaml

@@ -161,6 +161,12 @@
           heat: https://opendev.org/openstack/heat
     irrelevant-files: *base_irrelevant_files
 
+- job:
+    name: grenade-heat-multinode-skip-level
+    parent: grenade-heat-multinode
+    vars:
+      grenade_from_branch: stable/2025.1
+
 - project:
     queue: heat
     templates:
@@ -174,10 +180,12 @@
     check:
       jobs:
         - grenade-heat-multinode
+        - grenade-heat-multinode-skip-level
         - heat-functional
         - heat-functional-legacy
     gate:
       jobs:
         - grenade-heat-multinode
+        - grenade-heat-multinode-skip-level
         - heat-functional
         - heat-functional-legacy