Add gateway URL configuration to Hub Console

Allow changing the gateway connection URL at runtime via a new
PUT /hub/gateway endpoint and a corresponding input form in the
console UI.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/console/app.controller.ts

@@ -2,6 +2,7 @@ import {
   Controller,
   Get,
   Post,
+  Put,
   Delete,
   Param,
   Body,
@@ -23,6 +24,15 @@ export class AppController {
     };
   }
 
+  @Put("hub/gateway")
+  updateGateway(@Body() body: { url: string }) {
+    this.hub.reconnect(body.url);
+    return {
+      url: this.hub.url,
+      connectionState: this.hub.connectionState,
+    };
+  }
+
   @Get("agents")
   listAgents() {
     return this.hub.listAgents().map((id) => {