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.controller.spec.ts

@@ -4,6 +4,7 @@ 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 { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 
 describe("AgentsController", () => {
@@ -30,6 +31,11 @@ describe("AgentsController", () => {
     createHeartbeat: ReturnType<typeof vi.fn>;
     getRecentEvents: ReturnType<typeof vi.fn>;
   };
+  let messagesService: {
+    getMessages: ReturnType<typeof vi.fn>;
+    getReplayMessages: ReturnType<typeof vi.fn>;
+    getMessagesAfter: ReturnType<typeof vi.fn>;
+  };
 
   beforeEach(() => {
     // Create mock services
@@ -69,13 +75,20 @@ describe("AgentsController", () => {
       getRecentEvents: vi.fn().mockReturnValue([]),
     };
 
+    messagesService = {
+      getMessages: vi.fn(),
+      getReplayMessages: vi.fn().mockResolvedValue([]),
+      getMessagesAfter: vi.fn().mockResolvedValue([]),
+    };
+
     // Create controller with mocked services
     controller = new AgentsController(
       queueService as unknown as QueueService,
       spawnerService as unknown as AgentSpawnerService,
       lifecycleService as unknown as AgentLifecycleService,
       killswitchService as unknown as KillswitchService,
-      eventsService as unknown as AgentEventsService
+      eventsService as unknown as AgentEventsService,
+      messagesService as unknown as AgentMessagesService
     );
   });
 
@@ -365,6 +378,52 @@ describe("AgentsController", () => {
     });
   });
 
+  describe("getAgentMessages", () => {
+    it("should return paginated message history", async () => {
+      const agentId = "0b64079f-4487-42b9-92eb-cf8ea0042a64";
+      const query = {
+        limit: 25,
+        skip: 10,
+      };
+
+      const response = {
+        messages: [
+          {
+            id: "msg-1",
+            sessionId: agentId,
+            role: "agent",
+            content: "hello",
+            provider: "internal",
+            timestamp: new Date("2026-03-07T03:00:00.000Z"),
+            metadata: {},
+          },
+        ],
+        total: 101,
+      };
+
+      messagesService.getMessages.mockResolvedValue(response);
+
+      const result = await controller.getAgentMessages(agentId, query);
+
+      expect(messagesService.getMessages).toHaveBeenCalledWith(agentId, 25, 10);
+      expect(result).toEqual(response);
+    });
+
+    it("should use default pagination values", async () => {
+      const agentId = "0b64079f-4487-42b9-92eb-cf8ea0042a64";
+      const query = {
+        limit: 50,
+        skip: 0,
+      };
+
+      messagesService.getMessages.mockResolvedValue({ messages: [], total: 0 });
+
+      await controller.getAgentMessages(agentId, query);
+
+      expect(messagesService.getMessages).toHaveBeenCalledWith(agentId, 50, 0);
+    });
+  });
+
   describe("getRecentEvents", () => {
     it("should return recent events with default limit", () => {
       eventsService.getRecentEvents.mockReturnValue([