Interface GpuBvhRefitOptions

Read the stats back (a frame or two late) into latestStats, one small readback per copyStats the caller records. Off by default. ddgi-core promises hosts no readbacks frame after frame: its top level turns this on only in stats mode, and its deforming meshes copy at most once every 15 frames each (DECISIONS 2026-11-10). Correctness never depends on it: a refit that gives up is repaired on the GPU in the same frame either way.

Compiled pipelines to share with other refits. Without them each refit compiles its own in prepare. Why share: a caller with many trees (one per deforming mesh) needs one refit object each, for its own topology and parameters, but compiling the same kernels again for each would be a compile every time a mesh is added.