Studio grids: bring back the alternate row shading

Studio blocks are translucent now (white/60 on the gray page, white/6 on
black), so the shared gray-100/50 row tint vanished into them. Studio gets
its own black/4% (white/4% in dark) tint for bx-def-color-bg-hl rows.

Requested by AlexTr in #5679.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

template/css/tailwind.css

@@ -79,14 +79,17 @@
 
 
     /* Color Palette */
-    .bx-std .bx-def-color-bg-hl,
-    .bx-std .bx-def-color-bg-hl-even:nth-child(even),
-    .bx-std .bx-def-color-bg-hl-hover:hover,
     .bx-artificer .bx-def-color-bg-hl,
     .bx-artificer .bx-def-color-bg-hl-even:nth-child(even),
     .bx-artificer .bx-def-color-bg-hl-hover:hover {
         @apply bg-gray-100/50 dark:bg-gray-700/50;
     }
+    /* Studio: blocks are translucent (white/60 on the gray page, white/6 on black), where a gray-100/50 tint disappears; a black/white tint keeps the alternate grid rows readable. */
+    .bx-std .bx-def-color-bg-hl,
+    .bx-std .bx-def-color-bg-hl-even:nth-child(even),
+    .bx-std .bx-def-color-bg-hl-hover:hover {
+        @apply bg-black/[0.04] dark:bg-white/[0.04];
+    }
 
     .bx-artificer .col-red1 {
         @apply text-red-500;