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>

mindspace-content-scan.mjs

@@ -159,6 +159,14 @@ const TRUSTED_EXTERNAL_HOSTS = new Set([
   'images.unsplash.com',
 ]);
 
+export function replacePrivateResourceReferences(content, replacement) {
+  const source = String(content ?? '');
+  if (!source) return source;
+  const replacer =
+    typeof replacement === 'function' ? replacement : () => String(replacement ?? '');
+  return source.replace(PRIVATE_URL_PATTERN, (...args) => replacer(...args));
+}
+
 function inferFormat(content, format) {
   if (format === 'html') return 'html';
   return HTML_TAG_PATTERN.test(String(content ?? '')) ? 'html' : 'text';