fix(reliability): probe section existence via uci show, not an option key

payload/user/remote_access/pager-webui/server.py

@@ -4643,13 +4643,17 @@ PINEAPD_RUNTIME_UCI.add('pineapd.@ssidpool[0].disable')
 
 
 def _apply_uci_wanted(wanted):
-    """Idempotently apply a wanted UCI key/value set. Returns changed keys."""
+    """Idempotently apply a wanted UCI key/value set. Returns changed keys.
+    A failed `uci set` (e.g. missing anchor section) is NOT reported as
+    applied."""
     actions = []
     for key, value in wanted.items():
         rc, out, err = device_run(['uci', 'get', key])
         if rc != 0 or out.strip() != value:
-            device_run(['uci', 'set', '%s=%s' % (key, value)])
-            actions.append(key)
+            src_rc, s_out, s_err = device_run(
+                ['uci', 'set', '%s=%s' % (key, value)])
+            if src_rc == 0:
+                actions.append(key)
     return actions