fix(settings): persist latencyPing settings through native host round-trip

Add latencyPingEnabled and latencyPingIntervalMs to the native host
SETTINGS_DEFAULTS and updateSettings handler so they are persisted to
state.json and returned in the save response. Previously these fields
were extension-only and were silently dropped, causing the UI to revert
to defaults after every save.

native-host/holesail-manager/state.js

@@ -20,7 +20,9 @@ const SETTINGS_DEFAULTS = {
   disableOnFileUrls: false,
   backupRetention: 5,
   backupIntervalHours: 0,
-  tunnelAutoReconnect: false
+  tunnelAutoReconnect: false,
+  latencyPingEnabled: true,
+  latencyPingIntervalMs: 5000
 };
 
 const DEBUG = process.env.HOLESAIL_DEBUG === '1' || process.env.HOLESAIL_DEBUG === 'true';