style(ui): remove hover backgrounds from icon actions

src/ui/Button.module.css

@@ -71,7 +71,7 @@
   color: var(--fg-faint);
 }
 
-/* Toolbar / action buttons (ActionButton): transparent, rounded-square hover. */
+/* Toolbar / action buttons: transparent on hover, filled when pressed or selected. */
 .iconButton {
   flex: none;
   display: inline-flex;
@@ -88,7 +88,6 @@
   outline-offset: -2px;
 }
 .iconButton:not(:disabled):hover {
-  background: var(--bg-toolbar-hover);
   color: var(--fg-strong);
 }
 .iconButton:not(:disabled):active {