Implemented -zen-window-transform-origin attribute and applied it to the panels on the right side

src/browser/base/content/zen-styles/zen-panel-ui.css

@@ -6,6 +6,19 @@
 panel[type='arrow'][animate='open'] {
   @media (-moz-platform: macos) {
     animation: zen-jello-animation-macos 0.4s ease-out;
+    &[side='bottom'] {
+      /* Animate from the bottom */
+      -zen-window-transform-origin: 0 100%;
+    }
+    :root[zen-right-side='true'] & {
+      /* Animate from the right */
+      -zen-window-transform-origin: 100% 0;
+
+      &[side='bottom'] {
+        /* Animate from the bottom right */
+        -zen-window-transform-origin: 100% 100%;
+      }
+    }
   }
   @media (-moz-platform: linux) or ((-moz-platform: windows) and (not (-moz-windows-mica-popups))) {
     /* Mica popups have a weird background while the animation is running */

src/browser/base/zen-components/ZenGlanceManager.mjs

@@ -551,6 +551,8 @@
 
     async fullyOpenGlance({ forSplit = false } = {}) {
       this.animatingFullOpen = true;
+      this.#currentTab.removeAttribute('zen-glance-tab');
+
       gBrowser._insertTabAtIndex(this.#currentTab, {
         index: this.getTabPosition(this.#currentTab),
       });
@@ -558,7 +560,6 @@
       this._clearContainerStyles(this.browserWrapper);
       this.browserWrapper.removeAttribute('has-finished-animation');
       this.browserWrapper.setAttribute('animate-full', true);
-      this.#currentTab.removeAttribute('zen-glance-tab');
       this.#currentTab.removeAttribute('glance-id');
       this.#currentParentTab.removeAttribute('glance-id');
       gBrowser.selectedTab = this.#currentTab;