feat(FN-4649): complete Step 1 — add core task-created hook

Fusion-Task-Id: FN-4649
Fusion-Task-Lineage: 98ab6ec3-5253-4db6-93f0-de4ab7792002

packages/core/src/__tests__/task-creation-hook.test.ts

@@ -0,0 +1,107 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { setTaskCreatedHook } from "../task-creation-hooks.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+describe("task creation hook", () => {
+  const harness = createTaskStoreTestHarness();
+
+  beforeEach(async () => {
+    setTaskCreatedHook(undefined);
+    await harness.beforeEach();
+  });
+
+  afterEach(async () => {
+    setTaskCreatedHook(undefined);
+    await harness.afterEach();
+  });
+
+  it("fires once for createTask and createTaskWithReservedId", async () => {
+    const store = harness.store();
+    const hook = vi.fn();
+    setTaskCreatedHook(hook);
+
+    const created = await store.createTask({ description: "a" });
+    const reserved = await store.createTaskWithReservedId({ description: "b" }, { taskId: "FN-9101" });
+
+    expect(hook).toHaveBeenCalledTimes(2);
+    expect(hook).toHaveBeenNthCalledWith(1, expect.objectContaining({ id: created.id }), store);
+    expect(hook).toHaveBeenNthCalledWith(2, expect.objectContaining({ id: reserved.id }), store);
+  });
+
+  async function moveToDone(taskId: string): Promise<void> {
+    const store = harness.store();
+    await store.moveTask(taskId, "todo");
+    await store.moveTask(taskId, "in-progress");
+    await store.moveTask(taskId, "in-review");
+    await store.moveTask(taskId, "done");
+  }
+
+  it("fires for duplicateTask and refineTask", async () => {
+    const store = harness.store();
+    const source = await store.createTask({ description: "source", title: "Source" });
+    await moveToDone(source.id);
+
+    const hook = vi.fn();
+    setTaskCreatedHook(hook);
+
+    const duplicated = await store.duplicateTask(source.id);
+    const refined = await store.refineTask(source.id, "please refine");
+
+    expect(hook).toHaveBeenCalledTimes(2);
+    expect(hook).toHaveBeenNthCalledWith(1, expect.objectContaining({ id: duplicated.id }), store);
+    expect(hook).toHaveBeenNthCalledWith(2, expect.objectContaining({ id: refined.id }), store);
+  });
+
+  it("does not fire for applyReplicatedTaskCreate", async () => {
+    const store = harness.store();
+    const hook = vi.fn();
+    setTaskCreatedHook(hook);
+
+    await store.applyReplicatedTaskCreate({
+      replicationVersion: 1,
+      reservationId: "res-1",
+      taskId: "FN-9102",
+      sourceNodeId: "node-a",
+      createdAt: "2026-05-05T00:00:00.000Z",
+      updatedAt: "2026-05-05T00:00:00.000Z",
+      prompt: "# FN-9102\n\nreplicated\n",
+      input: { description: "replicated", column: "triage" },
+    });
+
+    expect(hook).not.toHaveBeenCalled();
+  });
+
+  it("swallows sync and async hook failures and still returns tasks", async () => {
+    const store = harness.store();
+    setTaskCreatedHook(() => {
+      throw new Error("boom");
+    });
+
+    const created = await store.createTask({ description: "a" });
+    const duplicated = await store.duplicateTask(created.id);
+    await moveToDone(created.id);
+    const refined = await store.refineTask(created.id, "feedback");
+
+    expect(created.id).toMatch(/^FN-/);
+    expect(duplicated.id).toMatch(/^FN-/);
+    expect(refined.id).toMatch(/^FN-/);
+
+    setTaskCreatedHook(async () => {
+      throw new Error("async boom");
+    });
+
+    const created2 = await store.createTask({ description: "b" });
+    expect(created2.id).toMatch(/^FN-/);
+  });
+
+  it("can clear hook with undefined", async () => {
+    const store = harness.store();
+    const hook = vi.fn();
+    setTaskCreatedHook(hook);
+    setTaskCreatedHook(undefined);
+
+    await store.createTask({ description: "a" });
+    expect(hook).not.toHaveBeenCalled();
+  });
+});