feat(orchestrator): add MS23 per-agent message history and SSE stream endpoints

GET /agents/:id/messages - paginated message history
GET /agents/:id/messages/stream - SSE live stream with replay

Partial #693

apps/orchestrator/src/api/agents/agents-killswitch.controller.spec.ts

@@ -5,6 +5,7 @@ import { AgentSpawnerService } from "../../spawner/agent-spawner.service";
 import { AgentLifecycleService } from "../../spawner/agent-lifecycle.service";
 import { KillswitchService } from "../../killswitch/killswitch.service";
 import { AgentEventsService } from "./agent-events.service";
+import { AgentMessagesService } from "./agent-messages.service";
 import type { KillAllResult } from "../../killswitch/killswitch.service";
 
 describe("AgentsController - Killswitch Endpoints", () => {
@@ -27,6 +28,12 @@ describe("AgentsController - Killswitch Endpoints", () => {
     subscribe: ReturnType<typeof vi.fn>;
     getInitialSnapshot: ReturnType<typeof vi.fn>;
     createHeartbeat: ReturnType<typeof vi.fn>;
+    getRecentEvents: ReturnType<typeof vi.fn>;
+  };
+  let mockMessagesService: {
+    getMessages: ReturnType<typeof vi.fn>;
+    getReplayMessages: ReturnType<typeof vi.fn>;
+    getMessagesAfter: ReturnType<typeof vi.fn>;
   };
 
   beforeEach(() => {
@@ -61,6 +68,13 @@ describe("AgentsController - Killswitch Endpoints", () => {
         timestamp: new Date().toISOString(),
         data: { heartbeat: true },
       }),
+      getRecentEvents: vi.fn().mockReturnValue([]),
+    };
+
+    mockMessagesService = {
+      getMessages: vi.fn(),
+      getReplayMessages: vi.fn().mockResolvedValue([]),
+      getMessagesAfter: vi.fn().mockResolvedValue([]),
     };
 
     controller = new AgentsController(
@@ -68,7 +82,8 @@ describe("AgentsController - Killswitch Endpoints", () => {
       mockSpawnerService as unknown as AgentSpawnerService,
       mockLifecycleService as unknown as AgentLifecycleService,
       mockKillswitchService as unknown as KillswitchService,
-      mockEventsService as unknown as AgentEventsService
+      mockEventsService as unknown as AgentEventsService,
+      mockMessagesService as unknown as AgentMessagesService
     );
   });