Add smart ACK provider for WeChat MP replies

Replace fixed ackText with a rule-based AckProvider that picks
response templates by message type and intent (translate, summary,
rewrite, poster, ppt, mindmap, code, search, schedule). Pure sync,
zero I/O, auto-falls back to config.ackText on any error.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

plaza-public.test.mjs

@@ -0,0 +1,17 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { renderPlazaPostRedirectHtml } from './plaza-public.mjs';
+
+test('plaza post shell embeds publication with resilient height sync', () => {
+  const html = renderPlazaPostRedirectHtml(
+    { id: 'post-1', title: 'Tall post', summary: 'A tall publication' },
+    'https://go.tkmind.cn/u/john/pages/tall',
+  );
+
+  assert.match(html, /src="https:\/\/go\.tkmind\.cn\/u\/john\/pages\/tall\?embed=plaza"/);
+  assert.match(html, /function measureFrameDocument\(\)/);
+  assert.match(html, /body\.children\.length/);
+  assert.match(html, /event\.source !== frame\.contentWindow/);
+  assert.match(html, /sandbox="allow-scripts"/);
+  assert.doesNotMatch(html, /sandbox="allow-same-origin allow-scripts"/);
+});