feat(config): persist config.patch updates atomically

src/gateway/server.ts

@@ -59,6 +59,8 @@ export interface GatewayServerConfig {
   authHttp?: boolean;
   uiDir?: string;
   config?: Config;
+  /** Optional persistence callback for config.patch updates. */
+  persistConfig?: (nextConfig: Config) => Promise<void> | void;
   /** Optional callback for system.restart. Should trigger graceful shutdown + process restart. */
   restart?: () => Promise<void>;
   channelRegistry?: ChannelRegistry;
@@ -193,7 +195,10 @@ export class GatewayServer {
 
     // Config handlers (only if config object is provided)
     if (this.config.config) {
-      const configHandlers = createConfigHandlers({ config: this.config.config });
+      const configHandlers = createConfigHandlers({
+        config: this.config.config,
+        persistConfig: this.config.persistConfig,
+      });
       for (const [method, handler] of Object.entries(configHandlers)) {
         this.router.register(method, handler);
       }