Revert "Declare a dark color scheme"

It did not remove the navigation flicker in Firefox; boosted navigation
will address it instead.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

assets/layout.html

@@ -3,10 +3,6 @@
     <head>
         <meta charset="UTF-8" />
         <meta name="viewport" content="width=device-width, initial-scale=1, interactive-widget=resizes-content" />
-        <!-- Dark from the first frame: browsers without cross-document view
-             transitions (Firefox) otherwise flash their default white canvas
-             between pages, before style.css applies. -->
-        <meta name="color-scheme" content="dark" />
         <title>{{.Title}}</title>
         <link rel="icon" href="{{asset "favicon.ico"}}" />
         <link rel="preload" href="/_/fonts/IosevkaEtoile.woff2" as="font" type="font/woff2" crossorigin />