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/task-creation-hooks.ts

@@ -0,0 +1,14 @@
+import type { Task } from "./types.js";
+import type { TaskStore } from "./store.js";
+
+export type TaskCreatedHook = (task: Task, store: TaskStore) => Promise<void> | void;
+
+let taskCreatedHook: TaskCreatedHook | undefined;
+
+export function setTaskCreatedHook(fn: TaskCreatedHook | undefined): void {
+  taskCreatedHook = fn;
+}
+
+export function getTaskCreatedHook(): TaskCreatedHook | undefined {
+  return taskCreatedHook;
+}