Cargo.toml: drops gbdt; adds memmap2 + approx; keeps ml-core only
(cannot depend on ml: would cycle since ml depends on ml-alpha for
the Mamba2 gate baseline).
build.rs: compiles 7 cubins (mamba2_alpha + 6 new placeholders)
with -O3 --use_fast_math --ftz --fmad. Skips kernels whose source
isn't present yet so partial check-ins work. Every env::var paired
with rerun-if-env-changed per the canonical build pearl.
src/pinned_mem.rs: local copy of MappedF32Buffer (mirrors
ml::cuda_pipeline::mapped_pinned::MappedF32Buffer). Drives the only
permitted CPU<->GPU path per feedback_no_htod_htoh_only_mapped_pinned.
Eventually the move-to-ml-core refactor will deduplicate; out of
scope for the Phase A branch.
Addendum: updates the import path to ml_alpha::pinned_mem.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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