feat(agent): stream live agent output to issue detail page

When an agent is working on an issue, users can now see real-time output
in the issue detail page instead of waiting for completion.

Backend:
- Add task_message table and migration for persisting agent messages
- Add POST /api/daemon/tasks/{id}/messages endpoint for daemon to report
  structured messages (tool_use, tool_result, text, error) in batches
- Add GET /api/daemon/tasks/{id}/messages for catch-up after reconnect
- Add GET /api/issues/{id}/active-task to check for running tasks
- Broadcast task:message events via WebSocket
- Daemon forwards agent session messages with 500ms text throttling

Frontend:
- Add AgentLiveCard component showing live tool calls, text output,
  and progress indicators with auto-scroll
- Wire into issue detail timeline with WS subscription and HTTP catch-up
- Card appears when agent is working, disappears on completion/failure

apps/web/shared/api/client.ts

@@ -32,6 +32,7 @@ import type {
   RuntimeHourlyActivity,
   RuntimePing,
   TimelineEntry,
+  TaskMessagePayload,
 } from "@/shared/types";
 import { type Logger, noopLogger } from "@/shared/logger";
 
@@ -309,6 +310,14 @@ export class ApiClient {
     return this.fetch(`/api/agents/${agentId}/tasks`);
   }
 
+  async getActiveTaskForIssue(issueId: string): Promise<{ task: AgentTask | null }> {
+    return this.fetch(`/api/issues/${issueId}/active-task`);
+  }
+
+  async listTaskMessages(taskId: string): Promise<TaskMessagePayload[]> {
+    return this.fetch(`/api/daemon/tasks/${taskId}/messages`);
+  }
+
   async getDaemonPairingSession(token: string): Promise<DaemonPairingSession> {
     return this.fetch(`/api/daemon/pairing-sessions/${token}`);
   }