In SCENE2D mode, how to remove the black edge of the map?

Sorry, I can't access https://community.cesium.com, so I'm asking here.

In SCENE2D mode, How to remove the black edges(shown in the following screenshot) or limit the camera to see only the region of the earth?

I tried to write an [example](https://sandcastle.cesium.com/#c=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), which seems to solve the problem, but when the camera is very far away from the ground, the map will shake.

```js
const viewer = new Cesium.Viewer("cesiumContainer", {
animation: false,
baseLayerPicker: false,
fullscreenButton: false,
geocoder: false,
homeButton: false,
infoBox: false,
timeline: false,
navigationHelpButton: false,
sceneMode: Cesium.SceneMode.SCENE2D
});

if (viewer.scene.mode === Cesium.SceneMode.SCENE2D) {
viewer.scene.preUpdate.addEventListener(scene => {
const maxCoord = scene.mapProjection.project(
new Cesium.Cartographic(Math.PI, Cesium.Math.PI_OVER_TWO)
);

const camera = scene.camera;
const frustum = camera.frustum;

const minX = -maxCoord.x - frustum.left;
const maxX = maxCoord.x - frustum.right;

const minY = -maxCoord.y - frustum.bottom;
const maxY = maxCoord.y - frustum.top;

camera.position.x = Cesium.Math.clamp(camera.position.x, minX, maxX);
camera.position.y = Cesium.Math.clamp(camera.position.y, minY, maxY);
});
}
```


Start by reproducing the linked Sandcastle example in Cesium.SceneMode.SCENE2D, especially at a far camera distance. The issue provides no repository file or test entry point, so investigation would need to trace the scene camera, map projection, frustum, and preUpdate behavior. Done would mean removing or limiting the black map edges without introducing visible map shaking.

Written by the indexing model from the issue text.