style(业务代码): 调大填色区域在视口中的缩放比例

- 横屏 rate 0.6 → 0.7，竖屏 rate 0.7 → 0.8
- 低分屏下填色区域更充分利用画布空间

src/base/Scene.ts

@@ -155,7 +155,7 @@ export class Scene implements Disposable {
     // this.resultMat[12] = tx
     // this.resultMat[13] = ty
 
-    let rate = this.width > this.height ? 0.6 : 0.7;
+    let rate = this.width > this.height ? 0.7 : 0.8;
     let scaleX = (this.width * rate) / this.contentWidth;
     let scaleY = (this.height * rate) / this.contentHeight;
     let scale = Math.min(scaleX, scaleY);