docs(FN-3887): clarify ntfy allowlist requirement for agent messages

- Update settings reference language for ntfy integration
- Clarify that agent messages require allowlisting configuration
- Keep notification setup guidance aligned with current behavior

Fusion-Task-Id: FN-3887

packages/engine/src/__tests__/message-notification-pipeline.integration.test.ts

@@ -0,0 +1,155 @@
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { beforeEach, afterEach, describe, expect, it, vi } from "vitest";
+import { Database, MessageStore, TaskStore } from "@fusion/core";
+import { NotificationService } from "../notification/notification-service.js";
+
+function makeTempRoot(): string {
+  return mkdtempSync(join(tmpdir(), "fn-msg-notify-pipeline-"));
+}
+
+describe("message notification pipeline integration", () => {
+  let rootDir: string;
+  let taskStore: TaskStore;
+  let messageDb: Database;
+  let messageStore: MessageStore;
+  let service: NotificationService;
+  let fetchSpy: ReturnType<typeof vi.fn>;
+
+  beforeEach(async () => {
+    rootDir = makeTempRoot();
+    taskStore = new TaskStore(rootDir, undefined, { inMemoryDb: true });
+    await taskStore.init();
+
+    messageDb = new Database(join(rootDir, ".fusion"), { inMemory: true });
+    messageDb.init();
+    messageStore = new MessageStore(messageDb);
+
+    fetchSpy = vi.fn().mockResolvedValue(new Response(null, { status: 200 }));
+    vi.stubGlobal("fetch", fetchSpy);
+
+    service = new NotificationService(taskStore, { messageStore });
+    await service.start();
+  });
+
+  afterEach(async () => {
+    await service.stop();
+    vi.unstubAllGlobals();
+    messageDb.close();
+    taskStore.close();
+    rmSync(rootDir, { recursive: true, force: true });
+  });
+
+  it("sends and suppresses agent-to-agent notifications according to runtime ntfy settings", async () => {
+    await taskStore.updateGlobalSettings({
+      ntfyEnabled: true,
+      ntfyTopic: "test-topic",
+      ntfyEvents: ["message:agent-to-user", "message:agent-to-agent"],
+    });
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "agent-B",
+      toType: "agent",
+      content: "hi from agent A",
+      type: "agent-to-agent",
+    });
+
+    await vi.waitFor(() => {
+      expect(fetchSpy).toHaveBeenCalledTimes(1);
+    });
+
+    expect(fetchSpy.mock.calls[0]?.[0]).toBe("https://ntfy.sh/test-topic");
+    const firstOptions = fetchSpy.mock.calls[0]?.[1] as RequestInit;
+    const firstHeaders = firstOptions.headers as Record<string, string>;
+    expect(firstHeaders.Title).toBe("agent-A → agent-B");
+    expect(String(firstOptions.body)).toContain("agent-A messaged agent-B: hi from agent A");
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "agent-B",
+      toType: "agent",
+      content: "reply preview",
+      type: "agent-to-agent",
+      metadata: { replyTo: { messageId: "msg-origin" } },
+    });
+
+    await vi.waitFor(() => {
+      expect(fetchSpy).toHaveBeenCalledTimes(2);
+    });
+    const replyHeaders = (fetchSpy.mock.calls[1]?.[1] as RequestInit).headers as Record<string, string>;
+    expect(replyHeaders.Title).toBe("Re: reply preview");
+
+    await taskStore.updateGlobalSettings({ ntfyEvents: ["message:agent-to-user"] });
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "agent-B",
+      toType: "agent",
+      content: "should be filtered",
+      type: "agent-to-agent",
+    });
+
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    expect(fetchSpy).toHaveBeenCalledTimes(2);
+
+    await taskStore.updateGlobalSettings({ ntfyEvents: ["message:agent-to-user", "message:agent-to-agent"] });
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "agent-B",
+      toType: "agent",
+      content: "enabled again",
+      type: "agent-to-agent",
+    });
+
+    await vi.waitFor(() => {
+      expect(fetchSpy).toHaveBeenCalledTimes(3);
+    });
+
+    await taskStore.updateGlobalSettings({ ntfyEnabled: false });
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "agent-B",
+      toType: "agent",
+      content: "disabled should suppress",
+      type: "agent-to-agent",
+    });
+
+    await new Promise((resolve) => setTimeout(resolve, 0));
+    expect(fetchSpy).toHaveBeenCalledTimes(3);
+  });
+
+  it("keeps agent-to-user notifications working", async () => {
+    await taskStore.updateGlobalSettings({
+      ntfyEnabled: true,
+      ntfyTopic: "test-topic",
+      ntfyEvents: ["message:agent-to-user", "message:agent-to-agent"],
+    });
+
+    messageStore.sendMessage({
+      fromId: "agent-A",
+      fromType: "agent",
+      toId: "user-1",
+      toType: "user",
+      content: "hello user",
+      type: "agent-to-user",
+    });
+
+    await vi.waitFor(() => {
+      expect(fetchSpy).toHaveBeenCalledTimes(1);
+    });
+
+    const request = fetchSpy.mock.calls[0]?.[1] as RequestInit;
+    const headers = request.headers as Record<string, string>;
+    expect(headers.Title).toBe("New message from agent-A");
+    expect(String(request.body)).toContain("agent-A → you: hello user");
+  });
+});