ci: add dashboard-description lint

Checks every grafana dashboard panel/board description against a length
cap and a small keyword list (operator name, tracker-tag references) so
the descriptions just shortened don't regress. Wired into both CI and
pre-push, same as the other content lints.

.forgejo/workflows/ci.yml

@@ -57,6 +57,17 @@ jobs:
       - name: lint
         run: sh scripts/check-attribution-trailers.sh
 
+  dashboard-descriptions:
+    name: dashboard-description lint
+    runs-on: [hive-ci]
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v3
+      - name: lint
+        # jq isn't a project dependency elsewhere in this repo — same
+        # nix-shell-for-one-tool shape the vale/shellcheck jobs above use.
+        run: nix shell nixpkgs#jq --command sh scripts/check-dashboard-descriptions.sh
+
   shellcheck:
     name: shellcheck
     runs-on: [hive-ci]