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/Hubs/Models/AgentStatusModels.cs

@@ -0,0 +1,92 @@
+namespace ControlCenter;
+
+/// <summary>
+/// Agent operational status derived from OpenClaw Gateway session activity.
+/// Maps to the frontend AgentStatus type: 'active' | 'idle' | 'thinking' | 'error'.
+/// </summary>
+public enum AgentStatus
+{
+    /// <summary>Agent is currently processing a turn.</summary>
+    Active,
+
+    /// <summary>Agent completed its last turn; no active work.</summary>
+    Idle,
+
+    /// <summary>LLM call in flight; tokens streaming.</summary>
+    Thinking,
+
+    /// <summary>Agent encountered an unhandled error.</summary>
+    Error
+}
+
+/// <summary>
+/// Extended lifecycle status including offline — not all agents have active sessions.
+/// Used internally; clients only see <see cref="AgentStatus"/> (offline maps to idle).
+/// </summary>
+public enum AgentLifecycleStatus
+{
+    Active,
+    Idle,
+    Thinking,
+    Error,
+    Offline
+}
+
+/// <summary>
+/// Pushed to SignalR clients when an agent's status changes.
+/// Matches the TypeScript <c>AgentStatusUpdate</c> interface from the design spec.
+/// </summary>
+/// <param name="AgentId">Agent identifier, e.g. "otto", "dex".</param>
+/// <param name="DisplayName">Human-readable name, e.g. "Otto".</param>
+/// <param name="Role">Role description, e.g. "Orchestrator Agent".</param>
+/// <param name="Status">Current operational status.</param>
+/// <param name="CurrentTask">Description of the current task, if any.</param>
+/// <param name="SessionKey">Full session key, e.g. "agent:otto:telegram:direct:8787451565".</param>
+/// <param name="Channel">Channel the agent is operating on, e.g. "telegram".</param>
+/// <param name="LastActivity">ISO 8601 timestamp of last activity.</param>
+/// <param name="ErrorMessage">Error message when status is 'error'.</param>
+public record AgentStatusUpdate(
+    string AgentId,
+    string DisplayName,
+    string Role,
+    string Status,
+    string? CurrentTask,
+    string SessionKey,
+    string Channel,
+    string LastActivity,
+    string? ErrorMessage = null
+);
+
+/// <summary>
+/// Pushed to SignalR clients when an agent's task progress updates.
+/// Matches the TypeScript <c>TaskProgressUpdate</c> interface from the design spec.
+/// </summary>
+/// <param name="AgentId">Agent identifier.</param>
+/// <param name="TaskDescription">Description of the current task.</param>
+/// <param name="Progress">Task progress percentage (0–100), if trackable.</param>
+/// <param name="Elapsed">Elapsed time string, e.g. "04m 12s".</param>
+public record TaskProgressUpdate(
+    string AgentId,
+    string TaskDescription,
+    int? Progress,
+    string? Elapsed
+);
+
+/// <summary>
+/// Snapshot of an agent's full card data, sent on initial connection
+/// or when the fleet state is requested.
+/// Matches the TypeScript <c>AgentCardData</c> interface from the design spec.
+/// </summary>
+public record AgentCardData(
+    string Id,
+    string DisplayName,
+    string Role,
+    string Status,
+    string? CurrentTask,
+    int? TaskProgress,
+    string? TaskElapsed,
+    string SessionKey,
+    string Channel,
+    string LastActivity,
+    string? ErrorMessage
+);