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>

mindspace-sandbox-mcp.mjs

@@ -17,6 +17,10 @@ import { execFileSync } from 'node:child_process';
 import mysql from 'mysql2/promise';
 import { createScheduleService } from './schedule-service.mjs';
 import { createScheduledTaskService } from './scheduled-task-service.mjs';
+import {
+  isScheduledTaskWorkerEnabled,
+  scheduledTaskWorkerDisabledMessage,
+} from './scheduled-task-worker-config.mjs';
 import { resolveScheduleTimestamp } from './schedule-time.mjs';
 import { shouldAutoCreateReminderAtStart } from './schedule-service.mjs';
 import { renderLongImage } from './mindspace-long-image.mjs';
@@ -1232,7 +1236,17 @@ async function callTool(name, args) {
         sourceMessageId: args.sourceMessageId ?? null,
         sourceText: args.sourceText ?? null,
       });
-      return [{ type: 'text', text: JSON.stringify(task, null, 2) }];
+      const workerWarning = isScheduledTaskWorkerEnabled()
+        ? null
+        : scheduledTaskWorkerDisabledMessage();
+      return [{
+        type: 'text',
+        text: JSON.stringify(
+          workerWarning ? { ...task, workerWarning } : task,
+          null,
+          2,
+        ),
+      }];
     }
     case 'scheduled_task_list': {
       const tasks = await getScheduledTaskService().listTasks({