polylineVolume Ignores Height when using CallbackProperty

PolylineVolume does not honor the position’s height when using a callback property. In the attached image, see two polylineVolume entities with the exact same shape and positions. The only difference is that the blue volume uses a CallbackProperty. Its height is ignored. The white one is rendered as expected.

This is a [Sandcastle example](https://sandcastle.cesium.com/#c=tVTRbtowFP2VqzwlEpjQlkmjgAYUiWlIqzZGH5Y+uMmFWDh2ZDuwdOq/z3EYDazTuofmwbm+Pufm+Fw7sRTawI7hHhUMQeAepqhZkZGVy/mRF7v5VApDmUAVecF1JCIRO2YuNTPMhpZ8IE6pMjai4pKslcxucKMQ9VgpWs6RbVKj/e+RAGi/D0nYgsuLaqzCZvJdNXZ7oX2OK1fPK3XyvqlEpzRHq8LVbuzjKOfCb7t6LajfQevvyP8F/hPXPgfeO+m18QSFsS6iJjRJ/J+uCs2wD5F3lzKD0IbUOQd7qbYaqAb8kWNsMIk899Fc8pLb7qwkLyqiqwHP3WnVc+fRIY6lst1clrmF/9Z7TJHJbDVbzG4O2IwaVIzyBpJLRe7mH5czsmcmHfM8pX5IesGBIQtT6emDUQWe5hz3rNJkMZ5+crAnOz4FrzNnwouGN2wjpMIE9ikKKDQTG5hSzh9ovL1VMkdlyle61T9t4mkN3w9gOGpYC2vKNQZvY/Fk8e3tHX6UMltKv1o88/z8RM+RJtbYW2bi9AsVG/TbXXdRQnLVsxe2G7rzHYng2mt5A21KjqNaG8AHluVSGSgU9wnpGMxybnetOw9FvEVDYq0rWRV00GlSBwnbAUuGL/yLIOZUa7uyLjj/yh4x8kaDjsX/QeXSSf+8Q8VpWcHS7mhRJwkhg46dvsw0UtoToM4q/wI) demonstrating the bug


Browser:
Chrome 112.0.5615.138
Firefox 112.0.1

Operating System:
Windows 11

Start with the linked Sandcastle example and compare the two polylineVolume entities, focusing on how the CallbackProperty supplies positions and height. Trace the polylineVolume update and rendering path, then add coverage showing that a callback-backed volume preserves the position height and matches the non-callback case.

Written by the indexing model from the issue text.