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>

src/utils/userAddress.ts

@@ -1,12 +1,16 @@
 import type { PortalUser } from '../types';
 
+function isInternalWechatUsername(value?: string | null): boolean {
+  return /^wx_[a-z0-9_]{4,64}$/i.test(String(value ?? '').trim());
+}
+
 export function resolveUserAddressName(
   user?: Pick<PortalUser, 'displayName' | 'username'> | null,
 ): string {
   const preferred = user?.displayName?.trim();
   if (preferred) return preferred;
   const username = user?.username?.trim();
-  if (username) return username;
+  if (username && !isInternalWechatUsername(username)) return username;
   return '用户';
 }