The animation tab's Fit frames the preview, and the separate Centre button is gone (#111)

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

src/editor/AssetTabEditor.ts

@@ -15,11 +15,14 @@ import {
 } from '../ui';
 import type { EditorState } from './state';
 
-/** The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much. */
+/**
+ * The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much.
+ * A canvas without `fit` belongs to a tab whose Fit frames something else (see `AssetTabEditor.fit`).
+ */
 export interface TabCanvas {
   readonly currentAssetId: string;
   show(assetId: string): void;
-  fit(): void;
+  fit?(): void;
 }
 
 export interface AssetTabOptions {
@@ -39,6 +42,7 @@ export abstract class AssetTabEditor<
 > extends VStack {
   /** Public for the check scripts. */
   readonly picker: Dropdown;
+  readonly fitButton: Button;
   protected readonly info: Label;
   /** Assigned by `mount`. Public because the check hooks and the play loop reach for it. */
   canvas!: C;
@@ -50,6 +54,7 @@ export abstract class AssetTabEditor<
   ) {
     super();
     this.picker = new Dropdown('—', { width: 200, onClick: () => this.openPicker() });
+    this.fitButton = new Button('Fit', { onClick: () => this.fit() });
     this.info = new Label('', { style: 'small', align: 'right' });
     this.info.minWidth = options.infoWidth;
   }
@@ -63,7 +68,7 @@ export abstract class AssetTabEditor<
     header.add(new Label(this.options.noun, { style: 'muted' }));
     header.add(this.picker);
     for (const widget of extras) header.add(widget);
-    header.add(new Button('Fit', { onClick: () => this.canvas.fit() }));
+    header.add(this.fitButton);
     header.add(new Spacer(), 1);
     header.add(this.info);
 
@@ -103,6 +108,11 @@ export abstract class AssetTabEditor<
     return canvas;
   }
 
+  /** What the header's Fit button frames. Override when the tab has more than one view. */
+  protected fit(): void {
+    this.canvas.fit?.();
+  }
+
   /** Enable/disable whatever `extras` the subclass passed to `mount`. */
   protected syncExtras(_asset: A | null): void {}