feat: Make close and reset icons only appear when hovering the tab, b=no-bug, c=folders, tabs

src/zen/folders/ZenFolders.mjs

@@ -1156,7 +1156,7 @@
       let dragDownThreshold =
         Services.prefs.getIntPref('zen.view.drag-and-drop.drop-inside-lower-threshold') / 100;
 
-      const dropElementGroup = dropElement;
+      const dropElementGroup = dropElement?.isZenFolder ? dropElement : dropElement?.group;
       const isSplitGroup = dropElement?.group?.hasAttribute('split-view-group');
       let firstGroupElem =
         dropElementGroup.querySelector('.zen-tab-group-start').nextElementSibling;

src/zen/tabs/zen-tabs/vertical-tabs.css

@@ -329,6 +329,13 @@
       scale: 0.92;
     }
 
+    &:not(:hover) {
+      .tab-close-button,
+      .tab-reset-button {
+        display: none !important;
+      }
+    }
+
     & .tab-icon-image {
       &:not([src]),
       &:-moz-broken {