ci: test against the PVE 9.2 ISO

The nested nodes were pinned to proxmox-ve_9.1-1.iso while production runs
9.2, so the suite was validating a PVE nobody uses. run-integration.sh already
reads PVE9_ISO with the 9.1 name only as a fallback, so this needs no script
change; setting it at the workflow level keeps provision and cleanup agreeing
on the ISO name, which force-cleanup needs to find the right file to delete.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/workflows/integration-tests.yml

@@ -70,6 +70,10 @@ env:
   # PVE 8 reached EOL 2026-08-31; CI provisions and tests PVE 9 only.
   # run-integration.sh still accepts "8" for local runs against old targets.
   PVE_VERSIONS: '9'
+  # Base ISO for the nested nodes. Set here rather than in run-integration.sh
+  # so provision and cleanup agree on the name — force-cleanup deletes the
+  # generated ISO by name and would miss it otherwise.
+  PVE9_ISO: proxmox-ve_9.2-1.iso
 
 jobs:
   # ── Build module artifact (GitHub-hosted) ────────────────────────