fix stuck tooltip bubble on safari

promote the [data-tooltip]::after pseudo onto its own compositor layer.
without this, the bubble's `display: block` state can latch on hover for
notification items where SubtleHover (also a promoted layer) shares the
stacking context.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/style.css

@@ -114,6 +114,11 @@ input:focus {
   white-space: nowrap;
   font-size: 12px;
   z-index: 10;
+  /* HACK: promote to its own layer so Safari's compositor doesn't latch the
+     bubble's `display: block` state when SubtleHover (also promoted) sits in
+     the same stacking context. Without this, hovering certain notification
+     items can leave the bubble visible permanently until a relayout. -sfn */
+  will-change: transform;
 }
 [data-tooltip]::before {
   content: '';