Reconciles the TerrainSystem against the authored Terrain each
frame, drives its per-frame update, runs the LOD compute, and publishes the
patch + indirect-args handles for the terrain shadow + G-Buffer features.
Owns the shared system's lifetime (destroys it on engine teardown).
Reconciles the TerrainSystem against the authored Terrain each frame, drives its per-frame update, runs the LOD compute, and publishes the patch + indirect-args handles for the terrain shadow + G-Buffer features. Owns the shared system's lifetime (destroys it on engine teardown).