cudarc 0.19 deprecated memcpy_stod (use clone_htod) and memcpy_dtov
(use clone_dtoh). Six call sites in cuda_pipeline/mod.rs migrated.
Pre-existing warnings surfaced now because the recent file-level
allow(unsafe_code) on this file no longer per-line-suppresses the
deprecated lint.
Per feedback_no_legacy_aliases: rename call sites directly, no
deprecated wrappers. Documented in dqn-wire-up-audit.md.