fix: remap CSS container rules from <main> to <article>

body > nav/header/article/footer all get container alignment
(max-width, auto margins, responsive padding). Replaces all
body > main selectors to match the new landmark structure.

assets/css/layers/00-reset.css

@@ -47,8 +47,8 @@ body {
 /* Prose font — same neo-grotesque stack, consistent across all contexts */
 /* article and [data-layout="prose"] inherit body font — no override needed */
 
-/* Main */
-main {
+/* Article as main content landmark */
+article[role="main"] {
   display: block;
 }