Use new styles from Figma for the color mode switch (#2217)

## Description

Ania updated the moon icon so it's not visually bigger than system and
sun and I don’t have to do `isSystemIcon ? "18px" : "16px"` anymore 🙏

The text is now smaller than in what we have on prod and there's a
little bit more padding.

Figma:
https://www.figma.com/design/aPUvZDSxJfYDJtPd7GF2sB/GraphQL.org--Working-File?node-id=6237-7449&t=C0utVsWrXtGCLTl4-4

<img width="250" height="161" alt="image"
src="https://github.com/user-attachments/assets/86ca0957-a37d-4e27-818c-601941a083b4"
/>
<img width="278" height="157" alt="image"
src="https://github.com/user-attachments/assets/86437a09-2e38-4677-b7ea-daeb5803b91a"
/>
<img width="137" height="141" alt="image"
src="https://github.com/user-attachments/assets/8cb8ceb7-6b56-4ac3-9ba2-63882cd67c36"
/>
<img width="160" height="165" alt="image"
src="https://github.com/user-attachments/assets/95383875-f542-4e9a-a424-864458a0e502"
/>

Author: hasparus

src/app/conf/_design-system/pixelarticons/moon.svg

@@ -9,6 +9,7 @@ import { useMounted } from "nextra/hooks"
 import MoonIcon from "@/app/conf/_design-system/pixelarticons/moon.svg?svgr"
 import SunIcon from "@/app/conf/_design-system/pixelarticons/sun.svg?svgr"
 import SystemIcon from "@/app/conf/_design-system/pixelarticons/system.svg?svgr"
+import CheckIcon from "@/app/conf/_design-system/pixelarticons/check.svg?svgr"
 
 const THEME_OPTIONS = ["light", "dark", "system"] as const
 export type ThemeOption = (typeof THEME_OPTIONS)[number]
@@ -49,41 +50,47 @@ export function ThemeSwitch({ lite, className }: ThemeSwitchProps) {
         aria-label="Change theme"
         title="Change theme"
         className={clsx(
-          "gql-focus-visible -m-2 flex cursor-pointer items-center gap-2 p-2 text-neu-800 transition-colors hover:bg-neu-50 hover:text-neu-900 focus-visible:!-outline-offset-2 dark:text-neu-700 dark:hover:bg-neu-50/50",
+          "gql-focus-visible relative cursor-pointer text-neu-800 transition-colors before:absolute before:-inset-2 hover:bg-neu-100 hover:text-neu-900 focus-visible:!-outline-offset-2 dark:text-neu-700 dark:hover:bg-neu-50/50",
           className,
         )}
       >
-        <ResolvedThemeIcon height="16" />
-        <Select.Value
-          className={clsx(
-            "text-sm capitalize leading-none",
-            lite ? "sr-only" : "text-neu-700",
-          )}
-        />
+        <div className="flex items-center gap-2 border border-transparent p-[5px] [[aria-expanded=true]>&]:border-neu-300 [[aria-expanded=true]>&]:bg-neu-0 [[aria-expanded=true]>&]:dark:border-neu-100">
+          <ResolvedThemeIcon height="16" />
+          <Select.Value
+            className={clsx(
+              "text-sm capitalize leading-none",
+              lite ? "sr-only" : "text-neu-800",
+            )}
+          />
+        </div>
       </Select.Trigger>
       <Select.Portal>
-        <Select.Positioner className="z-20 outline-none" sideOffset={4}>
-          <Select.Popup className="min-w-[var(--anchor-width)] border border-neu-200 bg-[rgb(var(--nextra-bg))] p-1 text-neu-900 shadow-md outline-none dark:border-neu-100">
+        <Select.Positioner
+          className="z-20 outline-none"
+          align="end"
+          sideOffset={4}
+        >
+          <Select.Popup className="w-[120px] min-w-[var(--anchor-width)] border border-neu-200 bg-[rgb(var(--nextra-bg))] bg-neu-0 text-neu-900 shadow-sm outline-none dark:border-neu-100">
             <Select.List>
               {THEME_OPTIONS.map(option => {
                 const Icon = OPTION_ICONS[option]
-                const isSystem = Icon === SystemIcon
                 return (
                   <Select.Item
                     key={option}
                     value={option}
-                    className="mt-px flex cursor-pointer items-center gap-2 px-3 py-1.5 text-neu-800 first:mt-0 focus-visible:outline-none focus-visible:ring-0 data-[highlighted]:bg-neu-100 data-[highlighted]:text-neu-900 data-[selected]:text-neu-600 dark:text-neu-700 dark:data-[highlighted]:bg-neu-50"
+                    style={{
+                      paddingBlock: lite ? "10px" : "9px",
+                    }}
+                    className="mt-px flex cursor-pointer items-center gap-2 px-2 text-xs text-neu-800 first:mt-0 focus-visible:outline-none focus-visible:ring-0 data-[highlighted]:bg-neu-100 data-[highlighted]:text-neu-900 dark:text-neu-700 dark:data-[highlighted]:bg-neu-50/50"
                   >
-                    <Icon
-                      height={
-                        // the icons are not fully proportional
-                        isSystem ? "18" : "16"
-                      }
-                      className={isSystem ? "-mr-0.5 -translate-x-px" : ""}
-                    />
+                    <Icon height={14} />
                     <Select.ItemText className="capitalize leading-none">
                       {option}
                     </Select.ItemText>
+                    <CheckIcon
+                      height={16}
+                      className="ml-auto hidden text-pri-base dark:text-pri-light [[data-selected]_&]:block"
+                    />
                   </Select.Item>
                 )
               })}