fix: Prevent sidebar from flickering when moving a tab, p=#12016

src/zen/compact-mode/ZenCompactMode.mjs

@@ -743,6 +743,10 @@ window.gZenCompactModeManager = {
             return;
           }
 
+          if (this._isTabBeingDragged) {
+            return;
+          }
+
           if (this.hoverableElements[i].keepHoverDuration) {
             this.flashElement(
               target,

src/zen/drag-and-drop/ZenDragAndDrop.js

@@ -105,7 +105,7 @@
 
     startTabDrag(event, tab, ...args) {
       this.ZenDragAndDropService.onDragStart(1);
-
+      gZenCompactModeManager._isTabBeingDragged = true;
       super.startTabDrag(event, tab, ...args);
       const dt = event.dataTransfer;
       if (isTabGroupLabel(tab)) {
@@ -874,6 +874,10 @@
         this._tempDragImageParent.remove();
         delete this._tempDragImageParent;
       }
+      delete gZenCompactModeManager._isTabBeingDragged;
+      if (dt.dropEffect !== "move") {
+        gZenCompactModeManager._clearAllHoverStates();
+      }
     }
 
     #applyDragOverBackground(element) {