收口前端平台组件库能力

新增 PlatformUiKit 通用弹窗、按钮、状态、空态、媒体、表单和标签等公共组件
迁移结果页、创作工作台、认证入口、RPG 暗色面板和运行态弹窗的重复 UI chrome
补充组件测试、页面回归测试、技术文档和 Hermes 共享决策记录

src/components/common/PlatformModalCloseButton.tsx

@@ -0,0 +1,65 @@
+import { X } from 'lucide-react';
+import type { ButtonHTMLAttributes, ReactNode } from 'react';
+
+type PlatformModalCloseButtonVariant =
+  | 'profile'
+  | 'profileCompact'
+  | 'floating'
+  | 'floatingPlain'
+  | 'platformIcon'
+  | 'editorDark';
+
+type PlatformModalCloseButtonProps = Omit<
+  ButtonHTMLAttributes<HTMLButtonElement>,
+  'children'
+> & {
+  label: string;
+  variant?: PlatformModalCloseButtonVariant;
+  icon?: ReactNode;
+};
+
+const PLATFORM_MODAL_CLOSE_BUTTON_CLASS_BY_VARIANT: Record<
+  PlatformModalCloseButtonVariant,
+  string
+> = {
+  profile:
+    'platform-modal-close flex h-9 w-9 items-center justify-center rounded-full',
+  profileCompact:
+    'platform-profile-icon-button flex h-8 w-8 items-center justify-center rounded-full',
+  floating:
+    'absolute right-3 top-3 z-10 flex h-8 w-8 items-center justify-center rounded-full bg-white/80 text-[#ff4056] shadow-sm',
+  floatingPlain:
+    'absolute right-3 top-2 z-10 flex h-8 w-8 items-center justify-center rounded-full text-[#ff4056]',
+  platformIcon: 'platform-icon-button',
+  editorDark:
+    'platform-modal-close-button--editor-dark rounded-full border border-white/10 bg-white/5 p-2 text-zinc-300 transition hover:bg-white/10 hover:text-white',
+};
+
+/**
+ * 平台弹窗关闭按钮。
+ * 收口个人中心和平台浮层里重复的关闭 aria、尺寸和视觉样式。
+ */
+export function PlatformModalCloseButton({
+  label,
+  variant = 'profile',
+  icon = <X className="h-4 w-4" />,
+  className,
+  type = 'button',
+  ...buttonProps
+}: PlatformModalCloseButtonProps) {
+  return (
+    <button
+      {...buttonProps}
+      type={type}
+      aria-label={label}
+      className={[
+        PLATFORM_MODAL_CLOSE_BUTTON_CLASS_BY_VARIANT[variant],
+        className,
+      ]
+        .filter(Boolean)
+        .join(' ')}
+    >
+      {icon}
+    </button>
+  );
+}