- Verified all phase PRs touch only `studio/backend/...` plus `scripts/`; no core training lib.
- Found GGUF NVIDIA path defaults to `SPEED_OFF` field but `resolve_speed_mode(..., is_gguf=True)` enables ~2.2x.
- Confirmed `SdCppEngine` not wired into live routes.
- COMPLETED: precise speedup matrix.
- PENDING: route CPU/MPS to sd.cpp.