[no-release-notes] /.github/workflows/bump-dependency.yaml: add client token check

.github/workflows/bump-dependency.yaml

@@ -5,7 +5,30 @@ on:
     types: [ bump-dependency ]
 
 jobs:
+  auth:
+    name: Authenticate Caller
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Check client token
+        env:
+          PAYLOAD_TOKEN: ${{ github.event.client_payload.token }}
+          EXPECTED_TOKEN: ${{ secrets.CLIENT_AUTH_TOKEN }}
+        run: |
+          set -euo pipefail
+          # refuse to proceed without a token
+          if [ -z "${PAYLOAD_TOKEN:-}" ]; then
+            echo "Unauthorized: missing token"
+            exit 1
+          fi
+          # simple equality check; doesn't echo secrets
+          if [ "${PAYLOAD_TOKEN}" != "${EXPECTED_TOKEN}" ]; then
+            echo "Unauthorized: bad token"
+            exit 1
+          fi
+          echo "Caller authenticated"
+
   get-label:
+    needs: auth
     name: Get Label
     outputs:
       label: ${{ steps.get-label.outputs.label }}