feat(settings): keep SyncGuard preferences in device-local storage

docs/settings.md

@@ -206,6 +206,8 @@ Setting key: syncGuardEnabled
 
 When enabled on this device, the workspace temporarily blocks interaction after a large batch of incoming note changes is detected during CouchDB LiveSync startup or resume. Incoming changes continue to be received and applied while the workspace is protected. The overlay can be bypassed at any time, including when synchronisation fails or the remote is unavailable. The preference is device-local; it does not affect other synchronising devices.
 
+Both SyncGuard preferences are stored in device-local storage for this Vault, separately from the main plug-in settings. They are not transferred through Setup URIs. Existing values saved by earlier test builds are migrated to device-local storage when the plug-in starts.
+
 The threshold avoids interruption for ordinary small transfers. However, the number of changes cannot be known before they arrive: some notes may be updated before the guard activates. The guard is a user-interface aid, not an atomic Vault snapshot or a restriction on other plug-ins and external tools. It does not apply to other remote types or to ordinary live changes after the initial catch-up.
 
 #### Minimum received files to protect the workspace