[Rendering] The bottom half of the skybox is completely hidden

Description:
In the latest snapshot, the bottom half of the skybox seems to be intentionally hidden or broken. When the player looks down from a high altitude, the normal dark gradient of the lower skybox is missing, and the stars that should be visible in that hemisphere are not rendering at all.

Steps to Reproduce:

1. Launch Minecraft 26.4-snapshot-6.

2. Create a world and set the time to night.

3. Fly to a high altitude and look straight down.

4. Observe that the lower half of the skybox (including the stars) is missing/hidden.

Expected Behavior:
The bottom half of the skybox should render normally with its dark gradient and stars (as it did in previous versions), instead of being hidden.