fix(wechat): avoid image_url session poison on report follow-ups

Store image-only WeChat messages without running Agent, scrub assistant image_url history, and retry historical-image failures with text-only prompts.

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

chat-image-turn-scope.test.mjs

@@ -103,6 +103,30 @@ test('scrubConversationHistoricalImageAttachments keeps only active turn attachm
   ]);
 });
 
+test('scrubConversationHistoricalImageAttachments removes assistant image_url parts', () => {
+  const { conversation, changed } = scrubConversationHistoricalImageAttachments(
+    [
+      {
+        id: 'assistant-old',
+        role: 'assistant',
+        content: [
+          { type: 'text', text: '已识别报告' },
+          { type: 'image_url', image_url: { url: 'https://example.com/report.png' } },
+        ],
+      },
+      {
+        id: 'user-new',
+        role: 'user',
+        content: [{ type: 'text', text: '解读报告，生成页面' }],
+      },
+    ],
+    'user-new',
+  );
+
+  assert.equal(changed, true);
+  assert.equal(conversation[0].content.some((item) => item.type === 'image_url'), false);
+});
+
 test('buildCurrentTurnImageScopeNote states one independent topic per upload', () => {
   const note = buildCurrentTurnImageScopeNote([
     {