PerceptionTrainer gains a `trunk: CfcTrunk` field constructed at the
top of `new()` (after the determinism seed guard). VSN's
weight tensors (`vsn_w_d`, `vsn_b_d`) now live on `self.trunk`; the
trainer-owned copies are removed. Forward + backward + AdamW access
sites redirect to `self.trunk.vsn_w_d` / `self.trunk.vsn_b_d`.
PRNG-state preservation: the trainer's ChaCha8Rng chain still draws
VSN values at the same call position as before, then memcpy_htod's
them into the trunk's zero-initialised VSN slots from X1. This keeps
every downstream weight (attn_q, ...) bit-identical to the pre-X2
layout — perception_forward_golden continues to pass with
max_diff = 0.000000.
Gradient buffers (`grad_vsn_w_d`, `grad_vsn_b_d`) and AdamW state
(`opt_vsn_w`, `opt_vsn_b`) remain at trainer level — they're
training-only and shouldn't move to the inference trunk.
Verification:
- perception_forward_golden: PASS (max_diff = 0.000000)
- ml-alpha lib tests: 34 pass
- alpha_train example builds clean
Per spec 2026-05-19-ml-alpha-v2-trunk-grows-and-deployability-design.md
§1.1, §2.2 (X2).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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