feat(CUB-19): implement AgentStatus SignalR hub for real-time updates

- Add AgentStatusHub with typed IAgentStatusClient interface
  - Hub at /hubs/agent-status (matches design spec)
  - Fleet group + per-agent group subscription
  - AgentStatusChanged and AgentTaskProgress push events
  - Extension methods for server-side push via IHubContext

- Add GatewayEventBridgeService background service
  - Connects to OpenClaw Gateway WebSocket (v3 protocol)
  - Handles challenge → connect → hello-ok handshake
  - Bridges sessions.changed, session.message, session.tool events
  - Translates Gateway session status to AgentStatus enum
  - Maintains in-memory fleet state for snapshot queries

- Add REST API controllers
  - GET /api/agents — fleet status snapshot
  - GET /api/agents/{agentId} — single agent status
  - GET /api/logs/{agentId} — agent session logs (stub)
  - POST /api/command/stop/{agentId} — stop agent
  - POST /api/command/restart/{agentId} — restart agent
  - POST /api/command/steer/{agentId} — inject message

- Add models matching TypeScript spec interfaces
  - AgentStatusUpdate, TaskProgressUpdate, AgentCardData
  - AgentStatus enum (active/idle/thinking/error)

- Configure CORS with credentials for SignalR WebSocket
- Configure Swagger/OpenAPI with XML doc comments
- Agent role map matching frontend AGENT_ROLES constant

backend/ControlCenter/Program.cs

@@ -0,0 +1,72 @@
+using System.Reflection;
+using ControlCenter.Hubs;
+using ControlCenter.Services;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// ── API Services ───────────────────────────────────────────
+builder.Services.AddControllers();
+builder.Services.AddEndpointsApiExplorer();
+builder.Services.AddSwaggerGen(c =>
+{
+    c.SwaggerDoc("v1", new()
+    {
+        Title = "Control Center API",
+        Version = "v1",
+        Description = "OpenClaw Control Center — Command Hub backend with SignalR real-time updates"
+    });
+
+    // Include XML doc comments in Swagger output
+    var xmlFile = $"{Assembly.GetExecutingAssembly().GetName().Name}.xml";
+    var xmlPath = Path.Combine(AppContext.BaseDirectory, xmlFile);
+    if (File.Exists(xmlPath))
+    {
+        c.IncludeXmlComments(xmlPath);
+    }
+});
+
+// ── CORS (kiosk + remote browser) ─────────────────────────
+// The Control Center frontend runs on a different origin than the backend.
+// SignalR requires credentials for WebSocket transport, so we use
+// specific origins rather than AllowAnyOrigin.
+var corsOrigins = builder.Configuration.GetSection("Cors:AllowedOrigins")
+    .Get<string[]>() ?? new[] { "http://localhost:4200", "http://localhost:5000" };
+
+builder.Services.AddCors(options =>
+{
+    options.AddDefaultPolicy(policy =>
+    {
+        policy.WithOrigins(corsOrigins)
+              .AllowAnyMethod()
+              .AllowAnyHeader()
+              .AllowCredentials(); // Required for SignalR WebSocket
+    });
+});
+
+// ── SignalR (real-time agent status updates) ───────────────
+builder.Services.AddSignalR();
+
+// ── Gateway Bridge Service ────────────────────────────────
+// Background service that connects to the OpenClaw Gateway WebSocket
+// and bridges events to the AgentStatus SignalR hub.
+builder.Services.AddSingleton<GatewayEventBridgeService>();
+builder.Services.AddHostedService(sp => sp.GetRequiredService<GatewayEventBridgeService>());
+
+var app = builder.Build();
+
+// ── Middleware ──────────────────────────────────────────────
+if (app.Environment.IsDevelopment())
+{
+    app.UseSwagger();
+    app.UseSwaggerUI();
+}
+
+app.UseCors();
+app.UseAuthorization();
+app.MapControllers();
+
+// ── Hub Endpoints ───────────────────────────────────────────
+// Agent status hub at /hubs/agent-status (matches the design spec)
+app.MapHub<AgentStatusHub>("/hubs/agent-status");
+
+app.Run();