优化: P1-a 长内容折叠(AI文本气泡+多冲突+错误堆栈)

- MessageList: assistant文本气泡>1500字符折叠(max-height 400px+渐变遮罩+展开按钮),流式中不折叠避免delta重排抖动(M1)

- ConflictResolver: 多冲突(>=3)默认折叠,点击展开diff(M6)

- HelpRequiredCard: context堆栈max-height 200px滚动+等宽字体(M7)

src/components/ai/HelpRequiredCard.vue

@@ -82,6 +82,11 @@ function handleSelectOption(opt: string): void {
   color: var(--df-text-dim);
   opacity: 0.9;
   word-break: break-all;
+  /* M7:context 含错误堆栈,长栈撑高卡片。等宽字体利堆栈行对齐;max-height + overflow-y:auto
+     短内容自动不显滚动条,长堆栈滚动扫看(比折叠实用,无需展开按钮)。 */
+  font-family: var(--df-mono, ui-monospace, SFMono-Regular, Menlo, Consolas, monospace);
+  max-height: 200px;
+  overflow-y: auto;
 }
 .ai-help-required-options {
   display: flex;