Shulkers cannot rotate their head more than 180 degrees

A shulker's head rotation is restricted to approximately 180 degrees when tracking nearby mobs, regardless of its orientation. It seems unable to rotate fully, limiting its tracking range to half of a circle.

Steps to Reproduce:

1. Summon a shulker in any orientation.
2. Observe the shulker’s head when it opens its lid and begins tracking nearby mobs.
3. Note that the head rotation is restricted to half of the full circular range.

Expected Behavior: The shulker should be able to rotate its head a full 360 degrees when tracking mobs.

Parity: Fixing this bug will make the shulker head rotation on par with Java edition.