fix: auto-recover WeChat agent sessions poisoned by dangling tool_calls

When a dedicated WeChat session history leaves unmatched tool_calls, the next reply fails with a 400 LLM validation error; detect that pattern and recreate the session before retrying.

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

wechat-mp.mjs

@@ -950,6 +950,15 @@ function isTopicResetIntent(text) {
   );
 }
 
+export function isRecoverableWechatAgentSessionError(message) {
+  const normalized = String(message ?? '').trim();
+  if (!normalized) return false;
+  if (/stale_session_poisoned_completion/i.test(normalized)) return true;
+  if (/403|404|not found|无权访问/i.test(normalized)) return true;
+  if (/tool_calls|tool_call_id|insufficient tool messages/i.test(normalized)) return true;
+  return false;
+}
+
 function normalizeNumber(value) {
   if (value === '' || value === null || value === undefined) return null;
   const num = Number(value);
@@ -1932,8 +1941,7 @@ export function createWechatMpService({
       return { sessionId };
     } catch (err) {
       const message = err instanceof Error ? err.message : String(err);
-      const mayBeStaleSession =
-        /403|404|not found|无权访问|session|stale_session_poisoned_completion/i.test(message) && sessionId;
+      const mayBeStaleSession = sessionId && isRecoverableWechatAgentSessionError(message);
       if (mayBeStaleSession) {
         sessionId = await ensureWechatAgentSession({
           userId: user.userId,