Add Hub Console with agent management and message routing

Implement Hub that auto-connects to Gateway, manages agents via REST API,
and routes WebSocket messages to agents by payload.agentId with echo responses
sent back to the original sender.

- Add Hub with GatewayClient auto-connect, agent CRUD, and message routing
- Add Console (NestJS) with REST API and static pages (management + demo client)
- Switch Gateway registration from explicit event to query-based on connect
- Remove deprecated types (RegisterPayload, metadata, SendMessagePayload)
- Add @nestjs/serve-static for serving console UI

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

src/console/app.controller.ts

@@ -0,0 +1,45 @@
+import {
+  Controller,
+  Get,
+  Post,
+  Delete,
+  Param,
+  Body,
+  Inject,
+} from "@nestjs/common";
+import { Hub } from "../hub/hub.js";
+
+@Controller("api")
+export class AppController {
+  constructor(@Inject("HUB") private readonly hub: Hub) {}
+
+  @Get("hub")
+  getHub() {
+    return {
+      deviceId: this.hub.deviceId,
+      url: this.hub.url,
+      connectionState: this.hub.connectionState,
+      agentCount: this.hub.listAgents().length,
+    };
+  }
+
+  @Get("agents")
+  listAgents() {
+    return this.hub.listAgents().map((id) => {
+      const agent = this.hub.getAgent(id);
+      return { id, closed: agent?.closed ?? true };
+    });
+  }
+
+  @Post("agents")
+  createAgent(@Body() body?: { id?: string }) {
+    const agent = this.hub.createAgent(body?.id);
+    return { id: agent.id };
+  }
+
+  @Delete("agents/:id")
+  deleteAgent(@Param("id") id: string) {
+    const ok = this.hub.closeAgent(id);
+    return { ok };
+  }
+}