fix(wechat): defer 45047/45015 delivery and control customer message budget

Persist formal replies when WeChat customer-service quota is exhausted,
claim them once on the next passive response, skip progress notices for
page generation, and suppress failure notices while a formal reply is pending.

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

wechat/customer-service-deferred.test.mjs

@@ -0,0 +1,69 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import {
+  composePassiveReplyWithDeferred,
+  createWechatCustomerServiceDeferredStore,
+  DEFERRED_DELIVERY_PRIORITY,
+  isWechatCustomerServiceQuotaError,
+  resolveDeferredDeliveryPriority,
+} from './customer-service-deferred.mjs';
+
+test('customer-service deferred store keeps one formal reply per openid', async () => {
+  const store = createWechatCustomerServiceDeferredStore();
+  const first = await store.upsertDeferred({
+    appId: 'wx1',
+    openid: 'openid-1',
+    priority: 'formal_reply',
+    content: '页面链接 https://example.com/page.html',
+  });
+  assert.equal(first.stored, true);
+
+  const lower = await store.upsertDeferred({
+    appId: 'wx1',
+    openid: 'openid-1',
+    priority: 'failure_notice',
+    content: '失败通知',
+  });
+  assert.equal(lower.stored, false);
+  assert.equal(lower.reason, 'lower_priority');
+
+  const claimed = await store.claimDeferred({ appId: 'wx1', openid: 'openid-1' });
+  assert.match(claimed.content, /page\.html/);
+  assert.equal(claimed.priority, DEFERRED_DELIVERY_PRIORITY.formal_reply);
+
+  const empty = await store.claimDeferred({ appId: 'wx1', openid: 'openid-1' });
+  assert.equal(empty, null);
+});
+
+test('customer-service deferred store replaces with higher priority content', async () => {
+  const store = createWechatCustomerServiceDeferredStore();
+  await store.upsertDeferred({
+    appId: 'wx1',
+    openid: 'openid-2',
+    priority: 'failure_notice',
+    content: '旧失败通知',
+  });
+  await store.upsertDeferred({
+    appId: 'wx1',
+    openid: 'openid-2',
+    priority: 'formal_reply',
+    content: '正式链接 https://example.com/new.html',
+  });
+  const pending = await store.peekDeferred({ appId: 'wx1', openid: 'openid-2' });
+  assert.equal(pending.priority, resolveDeferredDeliveryPriority('formal_reply'));
+  assert.match(pending.content, /new\.html/);
+});
+
+test('customer-service quota errcodes include 45047 and 45015', () => {
+  assert.equal(isWechatCustomerServiceQuotaError(45047), true);
+  assert.equal(isWechatCustomerServiceQuotaError(45015), true);
+  assert.equal(isWechatCustomerServiceQuotaError(40001), false);
+});
+
+test('composePassiveReplyWithDeferred merges fallback content', () => {
+  assert.equal(
+    composePassiveReplyWithDeferred('上一条结果', 'ack'),
+    '上一条结果\n\nack',
+  );
+  assert.equal(composePassiveReplyWithDeferred('', 'ack'), 'ack');
+});