runner: gpu AND cpu are now a node pool. Per-node cpu_slots (primary 3,
helpers 2, nodes.json-overridable); net stays primary-only. Python-less ops
(ffmpeg/ffprobe) now run remotely on the node's system python3. Verified: 9
concurrent ffmpeg_frames distributed 4 local / 2 m1 / 2 m4.
hunyuan3d_mlx: default to Studio-quality (octree 384, texture 4096, remesh
120k) — 4096 bake verified watchdog-free on M3 Ultra; big quality gain
(defined face, 120k faces). remesh_faces now a param. All param-overridable.
