fix(wechat): auto-repair missing share preview meta before page delivery

Pages with real HTML content but missing description, mindspace-cover, or
platform brand markers are patched in-place so WeChat link delivery no longer
fails after successful generation.

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

wechat-mp.mjs

@@ -2649,6 +2649,7 @@ export function createWechatMpService({
             bareCompletionReply,
             htmlGenerationNeedsRetry,
             replyHasPublicLinks,
+            topic: wechatIntent?.topic ?? intent?.agentText ?? '',
           });
           if (pageOutcome.action === 'session_retry') {
             throw new Error('stale_session_poisoned_completion');
@@ -2967,6 +2968,7 @@ export function createWechatMpService({
             bareCompletionReply,
             htmlGenerationNeedsRetry,
             replyHasPublicLinks,
+            topic: wechatIntent?.topic ?? intent?.agentText ?? '',
           });
           if (pageOutcome.action === 'session_retry' || pageOutcome.action === 'fail') {
             const text = pageOutcome.failureText ?? buildPagePublishFailureText();