Fix horizontal scroll in grid viewer: overflow-x on #main not body

body had overflow-x: hidden which ate the scrollbar.

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

public/style.css

@@ -99,6 +99,7 @@ nav {
 	flex: 1;
 	padding: 1.5rem;
 	width: 100%;
+	overflow-x: auto;
 }
 
 /* ===== SPLIT LAYOUT ===== */
@@ -1338,9 +1339,6 @@ nav {
 }
 
 
-.grid-viewer {
-	overflow-x: auto;
-}
 
 .grid-cells {
 	display: grid;