feat(frontend): add Test Suite management and Next Reply case editor

Replace the test-cases placeholder with suite list/detail flows, multi-select and drag reorder, and an edit-only single-step reply editor with keyword/LLM assertions.

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

frontend/src/components/editor/section-card.tsx

@@ -25,12 +25,15 @@ export function SectionCard({
   icon,
   title,
   description,
+  action,
   children,
   className,
 }: {
   icon?: ReactNode;
   title?: string;
   description?: string;
+  /** 标题行右侧操作区（如添加按钮） */
+  action?: ReactNode;
   children: ReactNode;
   className?: string;
 }) {
@@ -52,12 +55,13 @@ export function SectionCard({
                 {icon}
               </div>
             )}
-            <div className="flex min-w-0 items-center gap-1.5">
+            <div className="flex min-w-0 flex-1 items-center gap-1.5">
               <CardTitle className="text-sm font-medium leading-none">
                 {title}
               </CardTitle>
               {description && <HelpHint text={description} />}
             </div>
+            {action && <div className="shrink-0">{action}</div>}
           </div>
         </CardHeader>
       )}