LN_a gain/bias tensors now live at self.trunk.ln_a_gain_d / ln_a_bias_d.
Trainer-side initialization values still drive the upload, preserving
PRNG-driven init values. Gradient buffers + AdamW state remain at
trainer level.
Verification: golden bit-exact (max_diff = 0.000000); ml-alpha lib green.
Per spec 2026-05-19-ml-alpha-v2-trunk-grows-and-deployability-design.md §2.2 (X4).