fix(scheduled-task): enable worker by default and add WeChat preflight

Scheduled automations were saved but never executed because the worker
required an explicit env flag. Follow H5_REMINDER_WORKER_ENABLED when unset,
add WeChat preflight to write tasks deterministically, and surface worker
warnings on create.

Co-authored-by: Cursor <cursoragent@cursor.com>

scheduled-task-worker-config.test.mjs

@@ -0,0 +1,33 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  isScheduledTaskWorkerEnabled,
+  scheduledTaskWorkerDisabledMessage,
+} from './scheduled-task-worker-config.mjs';
+
+test('isScheduledTaskWorkerEnabled respects explicit flag', () => {
+  assert.equal(isScheduledTaskWorkerEnabled({ H5_SCHEDULED_TASK_WORKER_ENABLED: '1' }), true);
+  assert.equal(isScheduledTaskWorkerEnabled({ H5_SCHEDULED_TASK_WORKER_ENABLED: '0' }), false);
+});
+
+test('isScheduledTaskWorkerEnabled follows reminder worker when unset', () => {
+  assert.equal(
+    isScheduledTaskWorkerEnabled({ H5_REMINDER_WORKER_ENABLED: '1' }),
+    true,
+  );
+  assert.equal(
+    isScheduledTaskWorkerEnabled({ H5_REMINDER_WORKER_ENABLED: '0' }),
+    false,
+  );
+});
+
+test('scheduledTaskWorkerDisabledMessage only when disabled', () => {
+  assert.equal(
+    scheduledTaskWorkerDisabledMessage({ H5_SCHEDULED_TASK_WORKER_ENABLED: '1' }),
+    null,
+  );
+  assert.match(
+    scheduledTaskWorkerDisabledMessage({ H5_SCHEDULED_TASK_WORKER_ENABLED: '0' }),
+    /未开启定时自动执行 Worker/u,
+  );
+});