[signalapp/Signal-Desktop#7242] Allow collapsing archive sidebar

Co-authored-by: lukas <lukas.walter@aceart.de>

ts/components/leftPane/LeftPaneArchiveHelper.tsx

@@ -207,6 +207,11 @@ export class LeftPaneArchiveHelper extends LeftPaneHelper<LeftPaneArchivePropsTy
     );
   }
 
+  override requiresFullWidth(): boolean {
+    const hasNoConversations = !this.#archivedConversations.length;
+    return hasNoConversations;
+  }
+
   shouldRecomputeRowHeights(old: Readonly<LeftPaneArchivePropsType>): boolean {
     const hasSearchingChanged =
       'conversationResults' in old !== Boolean(this.#searchHelper);