Fix site margins: use 75% viewport width instead of fixed max-width

The fixed 1200px max-width left ~1/3 gutters on wide screens.
Now uses max-width: 75% so gutters are ~12.5% each side, with
full-width on mobile.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: deftio

docs/assets/css/style.scss

@@ -6,18 +6,21 @@ $on-large: 1280px;
 
 @import "minima";
 
-/* ── Wider content area with tighter margins ─────────────────────────── */
+/* ── Wider content area — ~75% viewport, ~12.5% gutter each side ─────── */
 
 .wrapper {
-  max-width: $content-width;
+  max-width: 75%;
   padding-left: 16px;
   padding-right: 16px;
+  margin-left: auto;
+  margin-right: auto;
 }
 
-@media screen and (min-width: 600px) {
+@media screen and (max-width: 768px) {
   .wrapper {
-    padding-left: 24px;
-    padding-right: 24px;
+    max-width: 100%;
+    padding-left: 16px;
+    padding-right: 16px;
   }
 }