fix(wechat): deliver failure notices and hot-swappable wechat-mp bundle

Notify users when HTML publish guards reject stub pages instead of silently
failing, send real page links when non-stub files exist, and split wechat-mp
into wechat-mp.bundle.mjs for fast production updates without full portal rebuilds.

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

server.mjs

@@ -157,7 +157,8 @@ import {
   WECHAT_NOTIFY_SUCCESS_V2,
 } from './wechat-pay.mjs';
 import { createWechatOAuthService, isWechatUserAgent, loadWechatOAuthConfig } from './wechat-oauth.mjs';
-import { createWechatMpService, loadWechatMpConfig } from './wechat-mp.mjs';
+import { loadWechatMpConfig } from './wechat-mp-config.mjs';
+import { loadWechatMpModule } from './wechat-mp-loader.mjs';
 import { validateWechatShareSignatureUrl } from './wechat-share.mjs';
 import { createScheduleService } from './schedule-service.mjs';
 import { createFeedbackService } from './user-feedback.mjs';
@@ -559,7 +560,8 @@ async function bootstrapUserAuth() {
       maxConcurrentRuns: Number(process.env.MEMIND_AGENT_RUN_QUEUE_CONCURRENCY ?? 1),
       runTimeoutMs: Number(process.env.MEMIND_AGENT_RUN_TIMEOUT_MS ?? 15 * 60 * 1000),
     });
-    wechatMpService = createWechatMpService({
+    const wechatMp = await loadWechatMpModule(__dirname);
+    wechatMpService = wechatMp.createWechatMpService({
       config: WECHAT_MP_CONFIG,
       userAuth,
       apiFetch: tkmindProxy.apiFetch,