feat(web): 前端共享基础(focusRing/proseBody/text-2xs + useBodyScrollLock + Toast撤销 + error/not-found/loading路由边界)

apps/web/lib/ui/variants.ts

@@ -23,6 +23,16 @@ export function cn(...classes: Array<string | false | null | undefined>): string
   return classes.filter(Boolean).join(" ");
 }
 
+// 统一焦点环（与 buttonBase 现有焦点环一致），供导航/输入等可聚焦元素复用。
+export const focusRing =
+  "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-cinnabar/35";
+
+// 手稿正文统一排版：衬线 18px、行高 1.9。
+export const proseBody = "font-serif text-[18px] leading-[1.9]";
+
+// Drawer / CommandPalette 共用的全屏遮罩。
+export const overlayScrim = "fixed inset-0 z-40 bg-black/30";
+
 const buttonBase =
   "inline-flex items-center justify-center gap-1.5 rounded border text-sm transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-cinnabar/35 disabled:cursor-not-allowed disabled:opacity-45";