ground_candidate answers (layer, chunk, band, cell) -> keep, x, z, scale, yaw, seed, wind from pure gf_*
steps and the density read between them; ground_fill draws its answers with the same operations in the
same order. A solid layer fills at step0 and band 0 whatever the camera, a far band drawing a stable
subset (draw 7 under (step0/step_b)^2), each thing an int id from (layer, chunk, cell), listed per chunk
into a caller's GroundSolids or answered by id. r3d_ground_clearing hands the trample over as discs.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
