docs(ci-syslog-watcher): document risk-acceptance for unvalidated rsyslog config copy

parts/linux/cloud-init/artifacts/ci-syslog-watcher.sh

@@ -8,6 +8,15 @@ status=$(cat /var/run/mdsd-ci/update.status)
 
 if [ "$status" = "add" ]; then
         echo "Status changed to $status."
+        # By design: the rsyslog config dropped here is not content-validated before being
+        # copied into /etc/rsyslog.d and loaded via `systemctl restart rsyslog` below. The
+        # trust boundary for this script is the /var/run/mdsd-ci directory itself, which is
+        # populated by the privileged Container Insights (mdsd/AMA) add-on via a hostPath
+        # mount - a component deployed and access-controlled outside this repo. Anything
+        # capable of writing into that directory already has node-level privilege equivalent
+        # to what this script could additionally restrict, so adding content validation here
+        # would not meaningfully reduce risk; the real control point is that add-on's
+        # hostPath/RBAC configuration, not this script.
         [ -f "/var/run/mdsd-ci/70-rsyslog-forward-mdsd-ci.conf" ] && cp /var/run/mdsd-ci/70-rsyslog-forward-mdsd-ci.conf /etc/rsyslog.d
 elif [ "$status" = "remove" ]; then
         echo "Status changed to $status."