Adds clone_to_device_{f32,i32}_via_pinned and upload_{f32,i32}_via_pinned
in `mapped_pinned.rs`. They allocate a temporary MappedXxxBuffer
(cuMemHostAlloc DEVICEMAP), write the payload via host_ptr, then async
DtoD into a target CudaSlice<T>. Used to migrate cold-path uploads off
explicit cudaMemcpy HtoD per `feedback_no_htod_htoh_only_mapped_pinned.md`
without changing struct field types where the kernel mutates the buffer
every step (e.g. portfolio_buf, weight buffers consumed by Adam).
Audit table updated in docs/dqn-gpu-hot-path-audit.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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