PerceptionTrainer's evaluate_batched + step_batched now read forward
kernel handles from self.trunk (snap_batched_fn, vsn_fwd_fn, ln_fwd_fn,
attn_fwd_fn, step_batched_fn, heads_grn_fwd_fn, transpose_3d_fn).
Trainer's duplicate cubin/function loading stays in place for now;
deferred dead-code cleanup.
Backward kernels (vsn_bwd_fn, ln_bwd_fn, etc.) stay on trainer — they
are training-only and don't belong on the inference trunk.
Verification:
- perception_forward_golden: PASS (max_diff = 0.000000)
Per spec §2.2 (X10b).
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