Add Stationery and Stationery Dark themes with notebook chrome.

Manila folders, ruled chat, post-it nav, and folder tabs; dark variant uses Catppuccin Mocha colors with muted stickies and soft glows.

src/app/components/sidebar/SidebarItem.tsx

@@ -7,6 +7,7 @@ export const SidebarItem = as<'div', css.SidebarItemVariants>(
   ({ as: AsSidebarAvatarBox = 'div', className, active, ...props }, ref) => (
     <AsSidebarAvatarBox
       className={classNames(css.SidebarItem({ active }), className)}
+      data-sidebar-item=""
       {...props}
       ref={ref}
     />
@@ -54,6 +55,7 @@ export const SidebarAvatar = as<'div', css.SidebarAvatarVariants & ComponentProp
     <Avatar
       className={classNames(css.SidebarAvatar({ size, outlined }), className)}
       radii={radii}
+      data-sidebar-avatar=""
       {...props}
       ref={ref}
     />
@@ -64,6 +66,7 @@ export const SidebarFolder = as<'div', css.SidebarFolderVariants>(
   ({ as: AsSidebarFolder = 'div', className, state, ...props }, ref) => (
     <AsSidebarFolder
       className={classNames(css.SidebarFolder({ state }), className)}
+      data-sidebar-folder=""
       {...props}
       ref={ref}
     />