Add pin_empty helper for empty scratch destinations.
The repeating pin_memory(torch.empty(...), make_copy=False) idiom hid a
full-size pageable template; pin_empty takes shape/dtype only.
Signed-off-by: tunji-ruwase_snow <tunji.ruwase@snowflake.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
