Tabs are open documents: Scene, Game and Plugins stay as fixed tabs, every other asset opens in its own tab (double click or Enter in the asset panel, on creation, from the list button), several assets of one kind can be open at once, a tab is labelled with its kind dimmed before the name, cut at 160 px and renamed with its asset, closes with its x or a middle click and goes away when its asset is deleted; a tab always shows its own document instead of following the selection, the picker in the tab head is gone, zoom and scroll are kept per document for the session and dropped on close, a double click on a call node stays in the same tab with breadcrumbs per tab; one editor per kind is switched between documents, the placement rules live in the pure module documents.ts, and the test hook showTab stays as a compatibility path; new e2e module 44 documents (#171)

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ui/widgets/Button.ts

@@ -23,7 +23,7 @@ export interface ButtonOptions {
 
 export class Button extends Widget {
   private readonly bg = new Graphics();
-  private readonly labelText: Text;
+  protected readonly labelText: Text;
   /** The label as set; `labelText` holds the possibly truncated version on screen. */
   private fullText: string;
   private pressed = false;
@@ -32,7 +32,7 @@ export class Button extends Widget {
   variant: NonNullable<ButtonOptions['variant']>;
   protected readonly align: NonNullable<ButtonOptions['align']>;
   protected readonly fixedWidth: number;
-  private readonly padding: number;
+  protected readonly padding: number;
   private readonly style: TextStyleToken;
   private readonly toggle: boolean;
   onClick?: () => void;