Make the viewport label size one setting

Scene labels used `small` (11 px), the Texture tab used `body` (13 px). Both now
read `Theme.viewportLabelSize` through two tokens that differ only in colour.

Dropping the per-frame `label.style.fill` assignment matters: textStyle() returns
shared cached instances, so with both views on one token it would have recoloured
the scene labels too.

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

src/editor/texture/TextureCanvas.ts

@@ -436,13 +436,12 @@ export class TextureCanvas extends Widget {
       return;
     }
     if (!label) {
-      label = new Text({ style: textStyle('body') });
+      label = new Text({ style: textStyle('viewportLabel') });
       this.labels.set(frame.id, label);
       this.labelLayer.addChild(label);
     }
     label.visible = true;
     if (label.text !== frame.name) label.text = frame.name;
-    label.style.fill = Theme.colors.text;
     const x = at.x + LABEL_INSET;
     const y = at.y + LABEL_INSET;
     label.position.set(x + LABEL_PAD, y + LABEL_PAD);