Promote ascii-frame-outer to GPU layer to stop hover blink

The body::before scanline overlay (position:fixed, z-index:9999) requires
the compositor to re-blend over the section every time a CPU repaint
happens inside it. Hover state entry/exit triggers these repaints, causing
a visible blink as the compositor flushes.

Fixes:
- Add will-change:transform + transform:translateZ(0) to ascii-frame-outer
  to promote it to its own GPU compositing layer, isolating its repaints
  from the scanline compositing pass
- Convert corner-pulse and subtle-pulse from text-shadow (CPU repaint)
  to opacity (GPU composited) to eliminate continuous repaint pressure
  inside the section

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

assets/css/dashboard.css

@@ -991,6 +991,8 @@ h1 {
     padding: 0;
     background: var(--bg-primary);
     margin-bottom: 2rem;
+    will-change: transform;
+    transform: translateZ(0);
 }
 
 .ascii-frame-outer::before {
@@ -1029,8 +1031,8 @@ h1 {
 }
 
 @keyframes corner-pulse {
-    0%, 100% { text-shadow: var(--glow-green); }
-    50% { text-shadow: var(--glow-green-intense); }
+    0%, 100% { opacity: 0.7; }
+    50% { opacity: 1; }
 }
 
 .bottom-left-corner {
@@ -1086,8 +1088,8 @@ h1 {
 }
 
 @keyframes subtle-pulse {
-    0%, 100% { text-shadow: var(--glow-amber); }
-    50% { text-shadow: var(--glow-amber-intense); }
+    0%, 100% { opacity: 0.75; }
+    50% { opacity: 1; }
 }
 
 .ascii-section-header::before {