v2.1 — Adapter rank-collapse fix (PR_eff 1.6 → 33). Bias accumulation control (‖mean‖₂ 16.4 → 8.6). ResidualSkipHead actor with learnable gate (1-layer-equivalent at zero-gate, free to open a non-linear branch). encoder_grad_source = td_only. New diagnostics (PR_eff, Cohen's d, actor_head_gate). CPU fallback for eigvalsh (MPS unsupported — was silently returning 0). PER-code cleanup (reg_cap removed). Composite test idx: −0.265 → −0.213 (~19% relative).
v2 — Initial release.