feat(wechat): add Intent Transaction Layer with unified task schema

Introduce Draft → Confirm → Commit flow for WeChat schedule intents behind
feature flags, plus h5_tasks dual-write/read aggregation and rollout scripts
so reminders and automations get explicit user confirmation before persisting.

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

scheduled-task-service.test.mjs

@@ -76,7 +76,7 @@ test('createTask returns existing active duplicate for same schedule', async ()
   let insertCount = 0;
   const service = createScheduledTaskService({
     async query(sql) {
-      if (sql.includes('FROM h5_scheduled_tasks') && sql.includes('status = \'active\'')) {
+      if (sql.includes('FROM h5_scheduled_tasks') && sql.includes("status IN ('active', 'locked')")) {
         return [[{
           id: 'task-existing',
           user_id: 'user-1',
@@ -125,6 +125,59 @@ test('createTask returns existing active duplicate for same schedule', async ()
   assert.equal(insertCount, 0);
 });
 
+test('createTask returns existing locked duplicate for same schedule', async () => {
+  let insertCount = 0;
+  const service = createScheduledTaskService({
+    async query(sql) {
+      if (sql.includes('FROM h5_scheduled_tasks') && sql.includes("status IN ('active', 'locked')")) {
+        return [[{
+          id: 'task-locked',
+          user_id: 'user-1',
+          title: '每日天气预报播报（上海+武穴）',
+          task_spec: 'running spec',
+          recurrence: 'daily',
+          hour: 8,
+          minute: 0,
+          weekday: null,
+          timezone: 'Asia/Shanghai',
+          next_run_at: 1780000000000,
+          last_run_at: null,
+          notify_channel: 'both',
+          status: 'locked',
+          attempts: 1,
+          last_error: null,
+          last_result_json: null,
+          source_channel: 'agent',
+          source_session_id: null,
+          source_message_id: null,
+          source_text: null,
+          created_at: 1780000000000,
+          updated_at: 1780000000000,
+        }]];
+      }
+      if (sql.includes('INSERT INTO h5_scheduled_tasks')) {
+        insertCount += 1;
+        return [{ affectedRows: 1 }];
+      }
+      return [[]];
+    },
+  }, {
+    clock: { now: () => 1780000000000 },
+  });
+
+  const task = await service.createTask({
+    userId: 'user-1',
+    title: '每日天气预报播报（上海+武穴）',
+    taskSpec: 'new spec',
+    recurrence: 'daily',
+    hour: 8,
+    minute: 0,
+  });
+
+  assert.equal(task.id, 'task-locked');
+  assert.equal(insertCount, 0);
+});
+
 test('cancelTask updates status to cancelled', async () => {
   const service = createScheduledTaskService({
     async query(sql, params) {